Indeed, green slime will help but you really need other o-rings.
- Losi 1/8" ones (the standard red/orange ones)
- Nortech Whities
- The rings janus_77 has, he has a gazillion of them
- Team Xtreme has some (expensive)
When building the shocks and want to be sure you don't damage the seals when inserting the shock shaft, put some thick grease or tape over the threads.
Or put the seals in some 100wt shock oil for a while, then apply green slime, let it rest for a few hours and then install the seals. But this may be a bit over the top
