lilbob -
some say that prop is best shot into a group that's just about to be worked... the increased bloodflow, some believe, makes the prop soreness easier to deal with.
This has never really worked for me, however... I find it's best to inject prop (cut down to <100mg/mL, preferably 50mg/mL) right AFTER the workout, when I've still got a pump on. I find it totally painless this way.
Talk to RADAR about the inject-then-workout strategy; I think he's tried it.
-M