Vinyl siding over concrete block
Own my own house I used strips of Advantec 3/4 subflooring, reason being is I had it on hard, it's not that expencive, far more water resestant then plywood or OSB.
I used 8" wide strips at the bottom, 6" wide in the corners, around windows and doors and the top, and 3" wide for the field. You need to do all the outside pieces and around the doors and windows first, then the field.
It also would be best to cover all your expost wood on the soffits with vinyl soffit and cover the fashias with coil stock before any siding goes on.
My slab was pored way to low so I used strips of coil stock bent 90 deg. along the bottom edge to help keeping water off the bottom edge, then I used 1 X 6 vinyl lumber along the bottom. That way the weed wacker will not hit the siding. It's best to run the vinyl lumber all the way to the outside corners so the vinyl corner sit on top of the 1 X 6 vinyl lumber.
On top Of that I put Z moulding, then J moulding.
Depending on how your windows and doors are trimmed now you may have to build out all the trim, and cover with PVC coil stock before siding.
I installed 3/4 foam to the walls between the strips but for a garage if you spaced the stips every 16" you should be able to get away without it.
We tryed using a ram set but my block was so poopy we had to use Tap Cons instead.
We used 1-1/4 roofing nails to hang the siding and they worked fine, Siding is hung not attached tight to the wall.
As soon as we finished people started stopping by that I had never met before and saying how much better it looked.