My preferred tools are a lacrosse ball & a step.
Put the ball on top of the step and let your calf sink into the ball. Roll the ball around the entire surface of the calf. If you can tolerate it, when you find a sore spot just sit and hold until that sensation alleviates.
Do not roll so hard that you are in agony as you can often create inflammation (or add to it) by doing this too aggressively.
I like to roll out the calf first followed by a calf stretch (see #stretchoftheweek #3). Try rolling each calf for a minute or two and then do a 30 second stretch 3 times (both legs). This would be a great routine post-run/exercise!