Bondo/body-filler working time (On Topic actually)

I tried using Bondo to make fillets and repair defects in some patterns
that I am making to cast. For this kind of fussy fiddling, the Bondo
sets up much too fast (3-4 minutes). Is there some way to increase the
pot life/working time? If I use less hardener, will that slow it, or
just screw it up? Is there something that I can add?
TIA,
Bob