The clam shell compressor looks like it will work if you can fit it around the front spindle when putting everything back together. I used two spring compressors, one on each side of the spring. heres a link to the
Compressors I used.
Like qwikbird said, you have to hold the shock piston while turning the nut. I had the same problem with one of the nuts being too rusted to get off: I ended up cutting the nut off with a dremel. g/l