Got a bit of rust starting up on my painted DB trailer. Want to nip that in the bud. What's the best product for a little touch up. Was looking at the rust fighting spray paints. Anybody had any expirence with these? Is one brand superior?

there is a product out there I think called Extend that reverses the rusting process..paint it on. check home depot

Are you planning on sanding? Rust is a nasty beast up here. I have been sandblasting a '73 SS El Camino for 2 weekends now and though you may think that's extreme, you'll be doing the same in time if you dont remove the rust before you paint. Even the rust inhibiting, or cold galv. paints require the rust to be removed(at least the bad stuff). Rust-oleum makes a rust reformer thats great for utility areas, but it leaves a texture that may not be suitable for a finish area. If you dont remove the rust it will come back and by that time it's pitted up good. I was told the best setup is clean bare metal and a self-etching primer. And as far as I know, sandblasting or sanding/grinding is the only way to remove ALL of the rust.

Go to an auto paint supply house and ask for a product called Rust Mort. This converts rust to a different compound, and actually becomes rust resistant. You brush or wipe it on and in about an hour it becomes a metalllic black looking stuff. Paint over that and you have it! Nothing beats sanding it off and a new paint job, or even maybe LineX for a more permanant solution.

20 years ago, I dissasembled a little super-rusty trailer and took all the pieces to Scott Galvanizing in Ballard. They hot-dipped the whole magilla for about $30. Then I re-assembled the trailer using all SS fasteners. I am still using that trailer for my alum boat and it looks as good now as when it was first done.

The hot-dip zinc places have an acid bath that completely takes care of the rust. they don't like paint, though.

good idea on hot dipping the trailer. There is a sand blasting place near Bothell where you could have it blasted to bare metal befor dipping. Sounds expensive though. Painted trailers are not for salt water

If anyone's interested in the hot-dip galvanizing, Scott Galvanizing did some work for me earlier this year. Came out nice. They charge 42 cents per finished pound, figure that whatever you dip will pick up 5% more weight worth of zinc.

If you want to do the job yourself there are a couple of ways to go about it.
The Rust-Mort that was mentioned earlier is a good way to go. You will need to wire brush off all scale rust and then apply. You can either brush it on, or in larger applications you can put it in a spritz bottle and spray it on. Once you apply it you will need to let is sit for 24 hours. It takes that long for the phosphoric acid to do its job. It will usually form a powder that you will need to wipe off with a damp cloth before painting. Once the water dries you can topcoat. Hammerite or a zinc rich (cold galvanizing) paint like AuntyM suggested would both be good ways to go.
Be warned that Rust-Mort has to be topcoated, if not it will rust again. If you dont want to topcoat then you will want to use Rust-Seal. It is made from the SEM company just like Rust-Mort but has a different chemical in it that forms a protective coating. Rust-Mort runs about $13 a pint, and Rust-Seal about $23 a pint.
The other methods require complete rust removal and spray equipment. Email me if you want to go over those.