The number one tip I received that helped so damn much is to thin the mud down. It's way too thick as purchased. You want it to be roughly the consistency of sour cream so it goes on thin and smooth.

The number 2 tip is to know when you're beat and pay for help. I started mudding my huge basement and realized it would take me weeks or months to complete. I paid a pro to do the rest and it was done in a week. Money well spent.

I think the brickwork looks fine. Why not start with a lighting upgrade instead?

I changed out the 2 standard LED bulbs in my garage for some fancy but cheap multi angled adjustable and very bright LED units. My garage went from a dingy hole to a glowing spacecraft docking port.