The Hopetech video shows the preference of using Hunter grease, but I have Fork Juice to hand - I understand it’s not the grease just a lube spray... will this have a negative effect on the piston seals?
red rubber grease available from motor factors or brake fluid. silicone spray probably would be alright but I won't risk it
There's a theoretical risk to the seal from the solvent/propellant entrained in the lube.
You can mitigate against this by letting it off gas by collecting the spray in something like the top of the spray can and letting it rest for a minute or two, then using the residue, which will be the bit you want anyway, to lube the seals and pistons with a pick, cocktail stick, a tooth brush or whatever.
That said, most propllants/solvents are so light they generally off gas very quickly. The risk of degrading seals is probably only real if you repeatedly spray them during their life.
I just bought what hope recommend, hunters silicone lube....
kinda expensive for a small bottle, but will probably last me years anyway...
this stuff, although I got it somewhere else....