+2, the best way to do it like K1w1t1m said is to measure from the top of your tube.Go with the lesser amount. I found out the hard way and blew one of the seals.
Search for progressive springs. I believe there is a page from Progressive that suggests to fill the forks to 5.5 inches from the top with the forks collapsed and the springs out.
What tool?replaced seals but not bushings.completely cleaned entire lower end. you would not believe the amount of dirt at bottom. leaning toward lower amount, if mushy could add more. old springs were still good. trying to figure way to add fluid to left without pulling cap,probably should have added when i had them on bench, thought injecting from bottom sounded good, but unable to find tool.