Framesaver

I'm thinking I might like to do something to try and rustproof the inside my newish cromoly frame after finding a rust stain on the seatpost when changing it out.

I've read about this stuff called JP Weigle Frame Saver but it seems only to be sold in the US. Is there an EU equivalent?

Do you have to fully strip a frame to apply and then rebuild?

Also, should I try and treat the rust spot on the inside where the seatpost was?

Cheers all.

I bought some from Ceeway a couple of years ago.
I sprayed it inside my frame before I built it up. I guess you could get it inside most tubes of a built bike, but with no bottom bracket or headset in you can be sure of getting in everywhere.
It's pretty simple stuff. Spray it in, bung the tubes up with kitchen roll or something, just to stop it dribbling everywhere, and leave it a while. I think the active ingredient is something like linseed oil, mixed with something to make it sprayable. Once you've coated the inside of the tubes with it, the solvent evaporates and leaves a coat of linseed oil on the inside of the tubes.