Rust Treatment - whats 'in' currently

[IainB]

Just purchased a W210 Merc which due to the brilliant build quality, needs a bit of rust treatment (yes...I know I 'should' cut out and weld new metal in, but its cold and wet out)

So....whats currently recommended in the rust treatment in a bottle stakes? Ideally something that will enjoy this wet weather, as I would like to do this now, rather than let the salt get into it

Also need to do a couple of patches underneath - anyone used the POR 15 products? Or again, whats recommended?

Thanks