My instructor didn't recommend crumb coating - but I read so much on this site about it. Is crumb coating the same as crusting? Would someone please help me out on this subject. Is it necessary and how do I tell when it has crusted? HELP! I'm so confused.

Most people crumb coat in order to seal in the crumbs on a freshly baked cake so that the crumbs don't appear on the finished iced surface.

I always crumb coat out of habit.

I lightly ice the cake with buttercream to the point where I can still see the color of the cake. I let it sit or refrigerate it at this point (because the crumb coat acts like a layer of saran wrap).

My icing only lightly crusts, but this just means that when you touch it, no icing comes up on your finger. When I go to put on the finish coat of icing, I get no cake crumbs on the surface this way. Another benefit can be that, especially in hot weather, the finished coat of icing is less likely to slide off of the cake sides.

HTH
Rae