A quarter inch drive should be pretty easy. Any quarter inch socket of whatever size could work - though you'll probably have to grind it to fit. To drive it, use an appropriate allen wrench. For instance, if you've got a quarter inch socket in 3/8ths, turn it upside down on the nipple, then drive it with a 3/8 allen. There are also quarter inch square drive adapters that are 1/4" square on both ends. You could drive that with your 1/4" breaker bar.
I don't know what the difference is between ATF and PSF (power steering fluid) but PSF works better than ATF with acetone.
I don't know what the difference is between ATF and PSF (power steering fluid) but PSF works better than ATF with acetone.