Cortisones or corticosteroids are the best drugs out there for reducing inflammation, but the sides are terrible. Fat retention, muscle loss, water retension, immune system degradation, and lethargy among others.
Muscle buidling is, in essence, inflammation of the muscle. If your intention is to reduce soreness from working out, I would reccommend a NSAID. Not to mention, high doses of fish oil work very well as a long term inflammation reducer.
If you, for some reason, are going to use Prednisone for something anyway, I would start dosing at 10-20mg once EOD. If that dose is not effective, move up the dose in 10mg increments. You're also going to suppress your adrenal cortex's production of cortisol with this, so you MUST taper off this drug.