Ok I'm working on a 5 tier wedding cake for tomorrow. I just crumb coated the bottom tier (14"), I have chocolate crumbs everywhere in the frosting...are they going to show through my fondant? Should I apply another layer of buttercream?

With practice, you can achieve a state of NO crumbs in your icing whatsoever. Take your time, swipe your spatula/bench scraper/knife whatever only in one direction, don't spread it on there like butter on toast. That pulls crumbs up and makes a mess. I wouldn't worry about it showing unless your crumbs are really "chunks", that stick out and make lumps. If you are nice and smooth all the way around, you should be fine.

My concern would rather be, is that crumbcoat thick enough so your chocolate cake isn't showing through your fondant? Like a slip showing through a sheer dress.....are you using white or light colored fondant over the dark cake?

I'm covering it with white fondant. The crumbs aren't chunky, I was going to maybe do the viva towel method to smooth it out before applying the fondant to make sure it was smooth...thanks for your help and suggestions

I'd put one more coat of buttercream but honestly a few crumbs aren't going to show through the fondant as long as the surface is not bumpy.

Bette safe than sorry right? Thanks so much