Where are the leaks? Down the barrel? Out the back? Around the valve halves... this is the same rt with the on off problem in the other thread right?
When I first gassed mine up (sat for 8 years) it leaked from every place it could. I bought a parts kit for $16 and replaced every oring no matter if it looked good or not. Still have enough for another rebuild from the kit.
It sounds like your on the right path, id just go through each section of the valve at a time. Clean/ new orings in the power tube, then clean/ new orings in the on off etc... use lots of oil and then shoot it about 30 times with the barrel off and all the excess will get shot out
keep us posted.
I know how the frustration goes. After not fiddling with my mag for almost a decade I tore it down and rebuilt it, put the on off pin in backwards, it would charge air till it leaked out the back and then when I pulled the trigger it sounded like the velocity was about 500fps, lol. You'll get it