Best way to touch up scratches in car paint?
 

What is the best way to touch up scratches in a car? They are too deep to buff out, so should I just use touch up paint purchased from the car dealer or is there some better alternative? How should the scratch and surface be primed/prepared before applying the paint?

If its through the clear and into the base color then your best bet is to purchase touch-up paint and layer it thinly into the scratch giving it some time to flash between coats. If its a very thin scratch you can sometimes cut the touch up paint with the appropriate thinner to make it apply easier and get deeper into the scratch.

The only real way to get rid of it is to have the panel repainted and then blended.

As for preparation you want to use a soap like Dawn to cut all the grease, wax, and protectants from the paint. It has to be as clean as possible. Do not let the soapy water sit on the paint for long and do not do it in direct sunlight. You don't want the soap drying on the paint.

Rinse well then dry it with a micro-fiber cloth and wait till its fully dry. Then start applying the touch-up paint in thin coats giving it time to flash ~5 minutes. Normally on a real paint job you'd wait 15-30 minutes, but this is a very small thin area so it will likely flash faster.

Keep on applying coats until its level with the paint surface then let it cure for a few days. If you want you can go back after that and wet-sand and buff it, but that is only if you want a perfectly smooth finish. this is the step that you will likely screw up on, and affect other area's of the paint if done wrong. When wet-sanding there can NEVER be enough water. Rinse the sanding block often. The water acts as both a lubricant and the frequent rinsing of the block removes paint debris so you aren't rubbing it back into the clear.

On the other side, a good detail shop can do all of this for you and buff the entire car for some money.

Could I just use a clay bar to clean the scratch area instead of dish soap?

Also does anyone know if its possible to remove stains from the plastic piece of a door? This stain was here when I bought the car and I haven't been able to figure out what to do with. I tried using some Back to Black but that didn't really do anything at all. It looks like whatever spilled on the vehicle must have bleached the plastic.

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Not much can be done with that except to re-dye the part black. which requires disassembly so the dye doesn't get on anything else.

As for the clay bar? You don't want to use it on scratches. Tiny bits of clay will get stuck in them, making it difficult to fill in the scratch and have the paint stick.

Your best bet is touch up paint, with maybe some thinner added to the paint to thin it out if the scratch is deep enough.

Stain is nasty. If strong all purpose cleaner and agitation with a detailing brush doesn't make a mark, next try IPA.

Best bet may be to contact a reputable detailer in your area as they'll have the experience, expertise and equipment to do that sort of repair to the paint and plastic - while it may be more expensive than doing it yourself, it'll definitely be cheaper than remedying a stuffup.