How important is it to paint with the wood grain, not against it?

We are painting some corn hole boards for my dad's birthday present. They are made of plywood and 2x4s. We did a coat of tinted primer and are now in the process of about a million coats of red...every time we let them dry, we end up with a 'roller spot' about 1/2 way down because they are too long to do a whole swipe.





I was just wondering if we could do the finishing stroke on the 2' side (which would be against the wood grain) or will that mess them up?How important is it to paint with the wood grain, not against it?
If you're using a roller and already have several coats on, it should be fine. Going with the grain matters when using a brush because of brushmarks, but not much with a roller.How important is it to paint with the wood grain, not against it?
You do want to go with the grain! Take a natural bristle brush and brush out the marks left by the roller while its still wet.