https://youtu.be/Kn6NVHLy-Xc
This video popped up on my feed (google spies) and looks like a good alternative to walnut blasting.
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Sandlapper BMWCCA #481069
07 e90 6AT, Cobb V3 protuned by Motiv, Aquamist HFS-4, DCI, ER CP/Tial BOV, AA DPs, AA Sport Intercooler, 19" BBS CH-R, Pure Stage 2 Turbos