After looking at the easily available solutions in Switzerland, I'm going:
- Evapo'rust to clean rust (Ordered through the Italian reseller Envirem).
- Motorex 466 as an anticorrosion waxy protective film. Our local equivalent of Weigle's frame saver I think.
- Seringes to inject solutions through vent holes.
I've also considered removing rust with an acid (Citric, oxalic, phosphoric…) instead of the Evaporust as I had citric and oxalic acid on hand. I liked that I could let the Evaporust soak for long to dissolve all flakes and surface rust without having to worry about dissolving the healthy steel too. From my cursory search evaporust really seems like a distinct product. A bit safer to handle than most acids and easy to soak without worrying about attacking paint or steel.
I've also considered other rust converters. The Swiss equivalent to polymer rust converters and primers is Brunox. I was less convinced by the examples I saw and didn't like the idea of a definitive plastic coating over some remaining rust flakes inside an inaccessible chain stay.
There are also lots of European companies with rust-removal and protection products, targeted mainly at the car restoration market:
- Germany: Fertan
- France: Ferose, Restom
- Another alternative to Weigle's Frame saver / Motorex 466: French Dinitrol. The correct French term for this family of products is: Cire anticorrosive pour corps creux (Antirust wax for hollow cavities). A search with those terms lead to a lot of easily available products.