If you're practicing for real steel, I think your best bet would be to save up for the actual pistol and buy snap-caps (i.e. dummy rounds that are meant to be struck repeatedly by the firing pin). Especially if your talking about the long double action trigger pull. A cheap revolver would provide an great platform for controlling the take up of the trigger pull.
I haven't run into any Airsoft replicas that have a trigger much like a real steel rifle/pistol trigger. (note...some of them are kind of close to light/target triggers in pull weight...but the takeup/break of real systems is just not the same).
The long double action pistols (i.e. 226/M9 92F) at least have a bit of trigger pull in double action...and the long sweep would help you learn to control the take up. Still...I suspect that the airsoft equivalent trigger pull would be less than half of what the avg real steel counterpart (or at least the pull feels really light in comparison).
However...if you're just practicing at home with stance/sighting/grip/etc...then an airsoft GBB is fine for casual stuff. There won't be much recoil, but there's enough feedback that you'll be able to see/get a sense for things. There won't be as much sighting vs. results feedback...I'd stick to the target pistol for honing those skills.
Remember however...crappy practice makes you perfectly crappy.