Try the Tamiya Light Curing Putty, no smell, cures instantly with a light, easy to sand. I use the UV light I have left over from a Bondic glue pen. I put a bit of putty on a notepad and cover it with a lid from a spray can so it doesn't start curing. Then start filling what you need, fill, cure, sand, all within a few seconds of each other. Working on the new 1968 Chevelle I filled the holes for the mirror and door handles within a couple minutes and that was 3 rounds of fill, cure and sand.