How to paint garage walls and floor

I built and finished a 600 sq foot garage. Walls internally are concrete block. I used a big chunky brush and hand painted them, I very quickly learnt that cheap masonry paint is not economical. It requires 3 coats, so not only do you lose loads of time but you end up spending the same if not more than buying good paint. I bought high quality masonry paint for the outside and the difference was massive, well worth the extra money. I used and would highly recommend Sandtex Masonry paint.

For the floor I got a DIY resin kit. It was a reasonably big job that took a few days (prep, primer, 2 colour coats, finishing) but it saved an absolute ton over paying a company. 600 sq feet was fairly easy. You could definitely do it by splitting your garage in half and tackling 1250 at a time. The resin cures quite fast, so if you go this route you will need at least 1 but ideally 2 or 3 spare hands on site to help

It’s easy. First, you get the paint and materials. Then, you hire a few guys, grab a lawn chair and a beer and supervise. 

What is the wall substrate?

Check out VCT for the floor. I don't know how well it will handle cold though. We don't have that shit in Long Beach.

In my garage build thread, I detailed how I applied Polycuramine to my floor. (It's basically an expensive DIY epoxy, but still far less expensive then having professionals do it.) Well worth the effort and outlay, but I had brand-new concrete. You might have to grind your floor down a little to get good results with this stuff (or any, for that matter).

https://www.vitalmx.com/forums/bike-builds/falcons-garage-build?page=2 
There are several posts about the floor paint process and the results. 

Being that the floors are stained, you will have to grind/sand/prime prior to applying paint, epoxy, glue down flooring, etc.

I have been remodeling the inside of my house for a while, doing all I can myself to save money.  When I finish the living area and get to the garage, this is going on the walls and ceiling of the garage:  PVC Wall & Ceiling Panels—Waterproof & Durable - Trusscore

I haven’t decided on the floor yet.  I did our 10,000 sq ft warehouse floor with Sherwin William’s industrial grade epoxy with color chips and it looks great and holds up well but I’m also considering Swisstrax for its ease of installation.
 

https://www.garagejournal.com/forum/ This was a rad page/forum back in the day but haven't been on it for years.

that's an understatement, getting the floors ground and acid bath is going to be by far the most important step in this job.  Home Depot rents the grinders, not a fun job at all but if there is going to be any chance that the new floor finish holds up then that's the most important step for sure.