Join Date: Jan 2012
Location: Walker, Louisiana
I think your results are typical for someone trying to accomplish what you were trying to do the way you tried to do it. Don't beat yourself up. A little extra finish work and they will look good.
Now the question to ask yourself now that you have done it this way.
Would the reveals really look so bad that it's worth all the effort it takes to make a biscuited or splined miter joints?
The answer is up to you. I think the rabbit would be a good compromise if you want to hide the side long grain of the perpendicular board.
Always prime first but anything that I have to assemble gets painted after assembly. That way I can sand and tweak and fill all I want with ease before the paint.
Again, don't beat yourself up. The amount of room for error on a long miter joint is pretty much nil.