Forums can be mirrored but there are too many 'unknown' variables involved
(i.e., the forum's size, the software the forum uses, is it an active forum,
etc.) to give you a proper answer. Each forum needs to looked at on an
individual basis as to whether or not it can be reasonably mirrored or not.

There is no "quick" step by step when it comes to mirroring forums.

Another consideration is whether the forum is one that allows embedded youtube
type videos in post. Painful that.