I've found the EC coating resin to be very good, even if a little expensive... I ad a little bit of graphite powder to thicken it slightly.  It makes a very hard and polishable surface on a plug, i normally wet sand it down to 1200 and polish it with polish and wax.

I've also very successfully used normal laminating epoxy with some filler and dye added ..  (micro glass balloons, graphite  and fumed silica)  The dye makes it easier to spot if you sand through to the next layer


 

"Sapere Aude"... Dare to KNOW!

The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...

103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)