I also like to inject before workout, then after I lift I massage the area in a hot shower. Best of both worlds, especially with short esters that cause lots of PIP.
timing normally doesnt matter except with something like test suspension.. a normal compound wont make a difference... it might somehow mentally for you but in reality it wont make a difference on most of them...
I don't time it to be on a workout day or anything like that. I just like to do it right after a shower. The muscles are warm and I am clean. Simple as that.