Exterior

1. Pre-wash: snow foam, left to dwell, to lift loose grit before anything touches the paint
2. Contact wash: two buckets, deep-pile mitt, rinsing the mitt after every panel
3. Decontaminate: iron and tar removers for bonded contamination shampoo cannot shift
4. Dry: high-GSM towel, patting rather than dragging
5. Protect: sealant or ceramic coating on a clean, dry surface

Grit being dragged across the paint, almost always during the wash rather than from the road.

A sponge holds the grit against the surface. A deep-pile mitt lets it fall into the fibres and away from the paint. Pre-washing with snow foam first removes most of the grit before you make contact at all.

Yes. Iron fallout from brake dust bonds to the paint and shampoo will not lift it. You can feel it as roughness after washing.

An iron remover dissolves it chemically, and you will see it turn purple as it works. Two or three times a year is enough for most cars.