No need, You can either spray primer over the bare metal. Allow to dry and then spray stonechip Shultz(?) from Hammerite Allow to dry and spray another coat as required.

Then up to you, you can paint the chassis in the car colour. 2 pack paint or an oil/gloss based paint thinned down with paint thinners, Again allow to dry. Its best doing over a week period.

I'd suggest if doing this do in the the garage and ensure plenty of ventilation, Making sure no cars are parked nearby. If needed Wickes sell paint mats you can mask to the garage door and hang down, holding the bottom down with some old tools.