I have blasted the bottom, on both sides of it. I plugged a couple pin holes by applying tape on the bottom, and put about 10 coats of wax on the drum plug it uses as a drain. I purchased the car tank kit, which mixes up to a quart and a half. It is THICK!!! Reminds you of honey, or thicker... kind of like Motor Medic or similar engine oil additive. I tried doing smaller amounts, but it became clear that I wasn't going to have enough to do the bottom and the first 1/3 of the sides (it has a ledge at that level which a container mounts to). Since the bottom was my main concern, I decided to just mix it all and pour it in. So far, it seems like it was the right thing to do. With the smaller amounts, I could see the "roughness" and waviness of the bottom. Now, it is filled and basically level (I leveled the tank when I let it set) with more than enough for me to ever have another problem.
The funny thing is, if you research the Novalac epoxies JimC posted, they say they can be used with some very, very nasty materials. However, there is a warning that comes with the sealer kit that says not to use things that contain mineral spirits....odd. I planned on letting in cure for quite some time, so I don't think this will be an issue. I have used a cheaper tank seal kit on our other parts washer that had identical pinholes, and many more of them, and it worked. We just cleaned the tank after a couple years of use and it is still hard as a rock with no leaks. I probably didn't need to use the more expensive kit on mine, but....its mine, not the shops!
Since I couldn't do the first third of the sides with the Novalac, I think I'm going to roll on about 3 heavy coats of SPI Epoxy. Worse case scenario, the first time I clean it and find out it didn't work, I just redo the first 3rd. The rest of the tank isn't submerged, so I don't think that'll be an issue.
I'll have to post some pictures as I go...