Any problem using Mag Wheel or Car Surface Polish for tumbler brass cleaner, even if it has petroleum additives?
Yes.
Most aluminum/alloy "cleaning/polishing" products contain fine abrasives and I do not want residual abrasive on brass surface scratching my dies. I also do not want products with acids as prolonged contact will leach zinc from brass to make it brittle with pink hue (Wet tumbling with some acid is OK as rinse water is used to dilute/rinse away acid from brass).
Most liquid brass polish products like Dillon, FA and others are well suitable for cleaning/polishing brass cases and I recommend them.
And while I happily used Brasso in the Army, I would not use it for brass cases. Brasso ingredient lists:
isopropyl alcohol 3–5%,
ammonia 5–10%,
silica (sand) powder 15–20% and
oxalic acid 0–3% -
https://en.wikipedia.org/wiki/Brasso
Brasso was formulated to remove tarnish by chemical reaction with copper and acid (Similar to adding Lemi Shine/lemon juice/citric acid to wet tumbling solution) with additional physical cleaning from fine silica/sand. While small amount of acid will just react with copper superficially, in larger amounts and over prolonged period of time, zinc could leach from copper enough to make brass brittle.
NuFinish "polymer" liquid polish is made from zinc cross-linking polymer emulsions and does not chemically remove tarnish (surface corrosion) from brass surface. And NuFinish does not contain wax that can be removed from brass surface rather create long-lasting polymer layer on brass surface that can help with resizing and prevent tarnishing for years (Why water beads on car paint surface even after several car washes or rain water on my car after a year) -
https://nufinish.com/faq/
Also, Brasso and rouge contain fine abrasives (NuFinish liquid polish does not) and I would not want to scratch my die surfaces with any residual abrasives on brass -
https://benchmarkabrasives.com/blogs/news/what-is-a-jewelers-rouge-and-color-chart
With walnut/corn cob media, I prefer to run the media on the "dry" side as adding too much polish will cause clumping of media to brass and will result in gray hue brass that are not clean or polished. After adding couple capfuls of NuFinish to new media, I will add another capful every few batches of brass to keep media on the dry side.
FYI, "... Best Way To Clean Brass?" article from Shooting Sports USA -
https://www.ssusa.org/content/what-s-the-best-way-to-clean-brass/