Clutch Cable & Vise Grips
I have a short (12") piece of nice thick clutch cable kinked in the middle such that it folds in half with a tight loop. I run the wire under the spring hook-end, pull it taut and grab both ends up close to the loop... clip the vise grips onto the cables without totally crushing it and I have formed a huge handle that I can easily leverage against the pipe (guarded by my hand) to pull the spring hook clear of the pipe loop. You only have to move the spring about 1/4" to get it off and maybe 1/2" to get it back on.
They make wonderful tools called spring hooks for a reason... they work. I like that the cable method because it gets me right up near the spring and no in-line high tension 6" to 9" away at the spring hook handle from pulling straight out the spring tools provide. My way keeps the drama to a minimum if the spring breaks while under tool tension. That and I just have to do things my way...