I have done 3 bottom jobs in the past year (2 H16's and 1 H14). I have used the West System epoxy with the fast hardener and the graphite filler ("to produce a low-friction exterior coating with increased scuff resistance and durability"). The graphite filler turns the epoxy jet black, and in my opinion eliminates the need to paint the epoxy.
If the bottoms are bad (require a few layers of glass and rebuilding of the original shape), I have used the hull template that Hobie provides to create a plastic scaper to run along the setting epoxy. You may need to add colloidal silica filler to increase the thickness of the mixture; this allows you to really rebuild the shape of the hulls.
Here is a link to the hull template:
http://www.hobiecat.com/support/images/ ... mplate.jpg
With an eletric sander and a little effort, you can remove old epoxy if need be and start again. In total (and after a bit of practice), it takes about 1.5-2 hours for us to do a bottom job...
Good luck
Jeffrey