I have spent forever looking for the coveted black trim pieces and pillars for my GTI both online and at the scrap yard. I'm not prepared to pay silly money for the parts so did some research, came across VHT vinyl dye which promised to dye the plastic parts, at £20 for two cans delivered I thought I would give it a shot, and the result is pleasantly surprising!
VHT dye can be found here, you want VHT SP942 (satin black) for an OEM look
I used my sunroof motor cover as a tester, this is before any prep
I cant stress how important the prep is for this paint, unlike normal paint it seeps into the plastic and physically changes the color, IT DOES NOT ADD A LAYER LIKE NORMAL PAINT. (and it does not need primer!!)First clean the part with dish soap and a scotch pad to get rid of all the detail products, grease and dirt that have built up.

Then use some 2000 grit wet and dry under running water (you can use some dish soap to help lubricate the surface some more). Dont be too rough, you don't want to ruin your plastic


A picture after prep, looks 100% better if you just wanted it stock!

Make sure the plastic is properly dry, then shake the paint. Shake some more. Shake a bit more. And a bit more for luck. This stuff needs to be properly mixed otherwise you might as well throw the part away after you paint it.
Apply really thin light coats with 10 minute intervals between each coat. This allows the dye to seep into the plastic. Too much and it will just sit on top of itself like normal paint and it wont seep in properlyAfter 1 pass:

After 2 passes:

After 3 passes:

After 4 passes:

Final result after 5th and final pass
:


Let it cure for 3 hours so far and can confirm that it looks like a genuine OEM part and whats better it doesn't chip, scratch or flake like normal paint so should be good for a few years wear and tear!!