I used Bilt Hamber products :- link below
I have previously used De-ox gel & dipping bath and Hydrate 80 on the chassis on my build prior to Hammerite. Its reasonable cheap and I left it on my TVR chassis and components for about 5yrs without painting we no sign of rust "re-growth"
They also do an Epoxy Mastic 2 part chassis paint which is the dogs naggers (but I already had a gallon of Hammerite)
Must say I am going off Hammerite it doesn`t seem to be as good as it used to....I think its all those tree huggers that have forced them to remove those chemicals that actually worked!
Bring back lead based paint!