My bookcase construction is done and I've got a coat of stain on it. I'm planning to brush on several coats of Polyurethane. I've heard, and it makes sense to me, that I should only apply brush-on finish to horizontal surfaces. In other words, finish one side, let it dry, turn the piece to the next side, and repeat. That way, I'll avoid runs and the finish will flow flat. That sounds great but what happens where the outside or inside edges meet. I doubt that I can finish the inside sides without getting at least some finish on the back or front (unless I used an artists brush and even then, I'm not that steady). The finish that I get on the other surfaces would create ridges that I would think would be visible and too hard to sand off without sanding through the stain. I'm sure spraying lacquer would be ideal but I like the durability of Poly although I'm not about to buy 100 cans of Poly spray either.
I'd be interested in hearing how any of you finish casework with brush-on Poly. What is your technique? Have you solved this problem?