maybe post a picture of how/what you are doing..
Not to be demeaning, but it really is as simple as you say you are doing. Just getting it all lined up. Bit more difficult with a Jack though, and one person. Are the bushing in correctly, and the correct ones - not too long or something interfering?
Personally, when working alone, I prefer to use a small shop crane (think engine hoist) and hang them. Much easier to position/maneuver around. Use rags under the straps/rope to protect the new paint. As well, mask up the leading edge of the door and edge of the fenders with some tape to help protect the fresh paint.
Give the paint some time to cure if it’s fresh.. it’ll leave marks with tape, rags, rope.. or banging into the fender, lol.
Just as an fyi, I’ve used many of those white metal bushings, and they never last. The hinge opening are usually oval at that point, and the cheap bushings don’t last. Big job, and not sure what you’re into for a project, but new hinges are the way to go - and drilling spot welds, welding, etc. Or alternatively, open them up and have new bushings turned out of impregnated brass, or anything else other than those cheap bushings. But, that’s a more involved suggestion.. just throwing out other ways there for you.