It depends a bit on the load, but for the most part small uncoated spots are just cosmetic. I've never observed any leading from those bare spots, and accuracy doesn't seem to be affected. An exception might be where two bullets stuck side by side and you have the full length of the driving bands uncoated.
If it's a situation where I want complete coverage, I'll give them two coats; that gives 99% of the bullets complete coverage. (The local indoor shooting range is one of those cases; they specify no exposed lead.)
For rifle loads (which I use at full power normally) I pretty much always use two coats, partly for full coverage and partly for the thicker coating. You may find that's not necessary.
