I 've used waxoyl, hammerite waxoyl underseal ,and Morris lubricants Ankor wax. ,not necessarily all at the same time
I think the hammerite underseal stuff can potentially be laid on too thick and when it cracks later could let water in and rust could start unseen under it so beware of that if using it.
I am impressed so far with Ankor wax , it shouldn't even need thinning as it has it's own solvent but if you leave the lid off too long or use a crap parafin gun to spray it on you might have to
It's made by Morris lubricants and i put a link to details of it on the 'Dirty D' thread in the My A series section .
I was told by a garage that works on old Citroens of all types from 2cv to DS GS and SM CX etc that Dinitrol is the top stuff ,but it's expensive .
That Bilt hamber stuff Neil put up looks interesting too.