Can you spray a finish? Most dining room tables are too big to be brushed applied, and for the reason you are experiencing. Instead of stripping, you may be able to sand out the brush stroked with 240 grit paper on an orbital sander. I would try that before stripping. Just be careful when sanding because you only want to even out the brush strokes and not actually go through the finish.
If you cant spray, I suggest rubbing the urethane on rather than using a brush. Hereís what you do. Thin the varnish 50% with mineral spirits. Then get yourself a clean cotton rag (old t-shirt material works great), and fold it into a nice square applicator pad. Wet the applicator with your mineral spirits and then dip it into your diluted finish. Wipe on smooth thin coats, overlapping the previous stroke with each pass by about half. This method will result in a super smooth finish with no bubbles and no brush strokes. But remember, you will need to apply twice as many coats to get to your desired film thickness. Because you are actually applying less material to the surface, the dry time is significantly decreased as well. So in some climates (hot and dry), youíll be able to apply as many as three coats per day. Just remember that when you use a wipe-on urethane, you arenít trying to flooding on a real thick layer. You are just coating the surface evenly with a thin wet film.
If you can spray, I suggest using a nitrocellulose lacquer or a precat lacquer, precat offering more durability. This type of finish is used on tables world wide by factories and alot of DIYers.