Tired of Body Filler Hardening Too Quickly?

i've painted and done body work many years, my first total paint job was a 67 dart in 1975 back in those days when you spread the filler you had to wait 15-20 minutes for it to set before you could sand, todays fillers i can't even get it spread before it set's. evercoats metal to metal gives plenty of time to work but it is harder to work with.