Timing doesn't really matter OP, someone said above they try not to pin a muscle that's just been trained...
I actually disagree with that a little.
The way I see it is: if a muscle is in recovery mode, it is in the process of utilising all the nutrition and rest that you are giving it. Why not pin that muscle and let it rest and recover when it has the chance.
I'm a firm believer in not pinning a muscle BEFORE it is trained. I don't want to agitate an area before I blast it. And as many people know, training a muscle with PIP can at times be unbearable.