: Now how agressively do I have to sand for epoxy thats cured for about a
: month? am I just roughing up the surface or really getting involved with a
: power sander?

Depends on what you're trying to do. If it's bumpy and you want smooth, you have to do whatever it takes to grind down the bumps - think I'd use a fairing board with 80-100 grit to try to avoid digging into the epoxy layers beneath the problem one. Fully cured epoxy resin is pretty tough stuff, as I've discovered when I've missed big drools on the topsides and had to try to sand 'em out afterwards. Time, patience and good sandpaper help a lot.

If you're just trying to create 'tooth' for another layer of epoxy or paint, we've found that a light hand-sanding with 120 grit, or even a fairly vigourous rub with a rough dry ScotchBrite pad, does the trick.
Above all, tho, make sure it's clean - no grease, oil (even from your hands), amine blush, etc. Thorough washing every step of the way takes time and effort, but can save a tonne of trouble over the life of the project.