Oh, those other mean birds! My mean birds did this to my Easter Egger -- she healed really quickly with lots of TLC. One thing I wish I'd done sooner was to find her a friend. In a couple of days, find your quietest bird to bond with him. This will make it a lot easier to fit him back with the flock. I didn't see how old he is or how many birds you have.
Boost his nutrition levels with lots of good things -- yogurt, poly-vi-sol children's vitamins without iron, hardboiled eggs, any kind of fish -- sardines are a big favorite here. I make mine a "casserole" of rice, broccoli and salmon.
Does he let you hold him? Talk to him in a soothing voice and pet him -- it will help calm him down. He may fuss at first, but eventually you will see him heave a "sigh" -- this is a good thing as it means he's accepted you as a friend and that he feels safe.
Dress his wounds with neosporin -- make sure there is no pain killer in it.
Let us know how he's doing?
Unless you are having a cold snap in Sunny California, your garage should be plenty warm for him. If you can comfortably stand in your garage with just shirt sleeves, no jacket, then the garage is plenty warm.
