Have you looked at shock seals for the seal kits? Thats where i get my seals and i use Kartek for the valves, but i use the RPG valves so i don't have to drill and tap the shock. If you don't use the schrader valves you need a needle and then you fill it like a basketball. Problem with that is there's no way to know exactly how much pressure you put in. I have to crank my regulator up to almost 300psi to get 200 in the shock and i always check it with a gauge when i'm done. Also, as the nitro tank gets empty, do you need to increase the regulator pressure? IDK schrader valves are the ONLY way to do it in my opinion.
If anyone knows how they do it on the Gen 2 shocks, i'd love to see that operation. Gen 2 only have a screw and an O-Ring so there's no way to put a needle in there and fill. I'd love to see the contraption that fills the shock and plugs the hole without losing any pressure.