I am trying to make a tierd cake , do you guys suggest I crumb coat and frost each layer before layering them? Or frost them all together? And how would I stack them already frosted? ?

Just put a stiff b/c dam on the first layer, add filling, then put the next layer on. Ice the whole thing @ one time. Should work fine.

Duplicate post, for other responses, please also see:

http://forum.cakecentral.com/cake-decorating-ftopict-593556-.html

HTH