You really gotta get in there to clean all the nooks and crannies...
We tried the fridge out for a couple of days to see how cold it got and how long it held the cold air. It wasn't getting below 55 degrees so we knew we had to add insulation. We bought a sheet of 1 1/2" rigid foam insulation board and cut it into panels to line the sides of the fridge. We also stuck a cork in the drain so that cold air couldn't escape through there either.
We coated the panels with white Easypoxy topside paint (because that's what we had laying around) and let it cure a few days before caulking them into place.
We caulked the seams as well (don't have a picture of it all completed), added weather stripping to the trim on the lid, and added a larger fan for circulation. The lid is still really cold on the outside so we try to keep something over it (I use a folded yoga mat) to insulate it a bit more. We should probably add some insulation to the inside of the lid at some point. But all in all, the fridge is running great! It stays around 40 degrees now. It also really helps to keep as much stuff in it as possible to hold onto the cold air. Oh and we got some handy little stacking baskets to try and help keep things organized in there.