User manuals usually have a lot of good info:

http://www.westsystem.com/webpages/userinfo/manual/

CLC and Nick have some good books about laying fiberglass too.

I assume you're using epoxy. Two or three layers is usually fine for wetting out at the same time. If you need to stage them, it's best to lay the next layer as soon as the prior layer is no longer tacky (best) or within 24 hours. Any longer and you'll have to sand a bit to get a good bond due to epoxy blush.