What grit before painting?

Primer surfacer is sanded dry with P320 to P400, with dust extraction – the mesh disc is the first choice here. What you want to see: matt, even, no shiny spots. Shiny spots are low areas that the paint will not level out.

Before top coat in light colours or metallic, finish finer at P500 to P600: otherwise coarse scratches show through the paint.

Sound old paint only needs to be matted: P400 to P600 dry or P800 wet. On edges, swage lines and corners use the non-woven abrasive – it sands without scratches and gets in everywhere.

Scuff plastic parts with P320 to P400 and light pressure, otherwise the plastic heats up and smears. Then adhesion promoter, then paint.

Vacuum or blow off the sanding dust, degrease with silicone remover and a clean cloth, then finish with a tack cloth. Do not touch the surface with bare hands after that – fingerprints show up in the paint as craters.

If you sanded wet, everything must be completely dry before painting, including folds and swage lines. Never wet-sand bare metal: it flash-rusts straight away.

Scratches you can still see under raking light before painting will almost always show in the finished paint – most clearly with metallic and dark colours. In that case go back one step and re-sand the whole area evenly with the finer grit, rather than just working the visible spot.