Best putty around is DYNATRON Puttycote.
It's a two part mix type that's a light blue in color. This stuff can be polished to a mirror finish. It drys in about 15 min. It also has some styrene fillers in it, so you can actually glue stuff to it with model glue. I learned about from my friend Bill Geary who has won some of the biggest contests in the USA. You won't find a better putty. It has to purchased at an Automotive Paint supplier. Check out this link on it.
DYNATRON Putty Cote