I have not tried an epoxy finish, so I cannot answer that question.
PROCEDURE FOR APPLYING A CA FINISH TO A PEN OR RING:
My process is overkill, but it works reliably for me on pens. (If it ain't broke, don't fix it.) It will work equally well on your ring:
* First and foremost, be sure to practice on prototypes before you try it on the pen/ring itself. If you are using a lathe, you can apply a finish to the non-completed project, then turn it off or sand it off and do another. You can keep going with finish practice until you are forced to stop and must actually finish the pen/ring.
* Shape the pen/ring as close to final as you can. Use tools or sandpaper as appropriate. Expect that the finish will build up a tiny amount. The best woodturners don't need much sandpaper, if any. I am not there yet.
* Mount the pen/ring on a slowly rotating tool. It should be slow enough that the CA won't be pulled away by centrifugal force from the pen/ring, or worse yet, flung off (eek!). I use a lathe on medium speed, maybe around 200 RPM, about 3 rotations per second. You might try a drill press on its side if it runs slow enough, or get a friend to help you jig-up a hand drill on slow. The pen/ring should not wobble as it rotates.
* Gently sand the rotating pen/ring with the five grits in a typical sanding pack: 150, 240, 320, 400, 600. Stop the rotating pen/ring and also gently sand with the grain. While stopped, wipe the sawdust and coarser grit off the piece with a clean cloth before proceeding to the next grit.
Note: You can do some final shaping with the lower grits.
WARNING: Your ring may sand unevenly because of the different hardness of the materials. Be aware and be careful.
I use the Rockler sanding packs. I stock up when they are on sale for $9.99, as they are now:
https://www.rockler.com/woodturners-multi-roll-sanding-pack
* Optional: Put on thin disposable gloves.
* Optional: If you are planning to apply stains, dyes, or oils directly to your pen/ring, do it now. Allow it to dry completely. I know some people who apply boiled linseed oil or tung oil or whatever first, but I don't bother. The CA finish can pop the grain without needing additional finishing products. I do not think it is necessary. (You can also dye your CA finish. GluBoost sells dyes for their CA finishes, and you can use other dyes, but I have no interest in trying them.)
* Apply standard GluBoost Fill 'n' Finish to the rotating pen/ring. I use 12x9 thin white craft foam sheets that I buy at Walmart for 88 cents apiece. Other people use paper towels (which absorb CA and sometimes smoke!), tiny plastic bags, or the fingertips from gloves to apply it. I cut a small piece and put two drops of CA on it. The CA will rest on the foam but not soak in. You may want to try one drop at a time for a ring. Use the craft foam to smooth the ripples and waves out of the finish. Your goal is a smooth coating. You have a little time. Be patient.
https://www.rockler.com/glu-boost-fill-n-finish
* Back away and gently spray GluBoost accelerator on the rotating pen/ring.
* Repeat the standard GluBoost Fill 'n' Finish coat. At this point, you will have applied two coats. Spray the accelerator again.
* Apply two or three coats of GluBoost Fill 'n' Finish Thin. Spray the accelerator between each coat.
* Polish with the nine Micro-mesh grits using the padded Micro-mesh, wet with water. I just toss 'em in a cup of water and pull them out one-by-one. Here are the grits: 1500, 1800, 2400, 3200, 3500, 4000, 6000, 8000, 12000. Don't press hard and be brief on each step, or you can remove the finish. After each grit, stop the rotating pen/ring and also gently polish "with the grain" to soften/remove circular scratches. While stopped, wipe the white swarf and coarser grit off the piece with a clean cloth before proceeding to the next grit.
https://www.rockler.com/micro-mesh-cushioned-abrasives
At this point, you can call it done.
* Optional: Final polish with Hut Ultra Gloss Plastic Polish. I found it at Woodcraft:
https://www.woodcraft.com/products/hut-ultra-gloss-plastic-polish
At this point, you will have a very hard, very durable, high gloss finish. I use GluBoost finish because I like the clear, sparkly look and ease of application. I also like that it is flexible and less likely to chip. You can achieve good finishes from other brands of CA.
ADDITIONAL NOTES:
* Satiny, More "Natural" Finish:
If you don't want a high gloss finish, you can stop at a courser grit of the Micro-mesh to get a more satiny, natural look. As I said above, practice on scrap until you find the look you like.
* Sanding a CA Finish:
Sometimes a CA finish doesn't work out. It may have ripples or bulges or whatever. Be sure your rotating tool is not turning too fast when you apply the CA. If you do get finish problems, you can sand it down and try again. Don't worry about the white scratches in the CA that hide your beautiful work. They will disappear when you apply a new CA finish.
* TIGHT BUDGET:
Yeah, it is a lot of money for finishing one ring. You can use the materials to finish future projects, of course. CA glues last six months to a year if kept in a cool dry place. If you must economize:
+ Use less fancy sandpaper, but try to find a similar combination of grits.
+ Use a different CA for a finish. Any brand of CA glue will work and you will get different opinions about good and bad. You might get away with one bottle of flexible CA (preferred to avoid chipping), or medium CA. If you are patient, you can skip the accelerator/activator and let the CA cure on its own. It still takes only a few minutes for each coat.
+ Don't skip the Micro-mesh. I have not found anything else quite like it. There may be other less expensive competitors.
I hope this level of detail helps you and others. I need to find a way to better organize these tomes, besides leaving them as simple posts in forums. :-(