I use a roll around battery charger that goes up to 200 cranking amps. It has different settings from 10, 40, and start assist which is the 200amp setting. Ive tried it on 40 and it didn't do any better than at 10. I only use 10amp now. Yes, you are correct, it does seem to take forever but I normally start in the AM and leave it over night outside in the covered washbay at work. Like the oil pan I put it in Tuesday at about 3pm and took it out today at 330. I used the garden hose to remove the paint and primer and it peeled of in a big PLOP. Then the pressure washer removed the rest. The black that's in the bottom was over the entire inside but it all came off except in the corners. I hope this helps some but I will take some pics of it in the AM. Thanks for all the interest.
By the way, you can see my barrel behind my OlRustyCrank on the first page. Ill get some better one tho