The process was:
mix together putty
roll it out as flat as possible, use olive oil so it doesn't stick to the roller
Cut out a rectangular shape from it
Flatten that as much as possible
apply to models
being an amateur at this naturally I got fingerprints all over it, which I smoothed-ish with one of the many sculpting tools (still don't know what half of them are for).
The amount of putty I used was about 3 inches for 12 models and there was some left over, I think that I did a good job, but some models did turn out to look too bulky, or the cloak was too short, but overall I'm happy.
the whole group:
Next is basing, then another spraying session! Which will included more models this time.