Yeah, sort of. I mix up the 2 part epoxy as normal then add the graphite powder and continue stirring. I don't think I've got the data from my test pieces any more when I was finding the best ration of epoxy to powder so this winter when I'll be recoating the kayak hull I'll have to do some more test pieces. Deep joy.
I use lots of different 'fillers' with epoxy, depending on the job, silica, micro balloons, silica/micro balloon mix (the silicar makes it smoother), sawdust, fibreglass powder. It's a pretty versatile substance, epoxy resin, basically a coating but with the right filler in the right ratio it's a fantastic glue - but not for plastics.