Paint advice needed

[puddlesurfer]

I would like to paint the underside of my truck to stop it rusting any further.

I can give it a bit of a rub down using a wire brush to get the worst of the flaky stuff off and then jet wash it - but there is still going to be some rust I'll never get it back to pristine metal

What would people recommend to paint it with? I think I'll use a paint brush rather than sprays.

[markp2]

Have a look at http://www.rust.co.uk/
I have coated the underside of mine with their Milspec waxy gunk. It dries to the touch and is much less messy than Waxoyl. I intend to do the inside of the chassis as well, but haven't got round to it yet.
Mark