I've tried a few methods of removing ball swirl, and I think I've found the right process after checking on pins I've done over a year or more ago.
Both products are CHEAP and you can get them at any supermarket;
ISOCOL - Green plastic bottle with a croc on the front of it $5 - $8
Chux Magic Eraser - $3 for a pack of 8
Removing Ball Swirl
TIP - Clean the playfield with SHELLITE (Naptha) - and the Magic Eraser pads last heaps longer. All the surface dirt and wax will clog the ME.
Squirt the ISOCOL into the ME pad, and then press the pad against the playfield and then scrub the area with LIGHT pressure in a circular motion. Turn the pad over frequently and check the dirt is being removed from the playfield... Don't scrub too hard, or you could lift paint. A white residue is left behind - this is normal. Just wipe the affected area with ISOCOL on a rag.
One thing I picked up during the Flash playfield clean - If you have straight lines in the playfield - especially in the white areas where the plastics sit - run the ME in the area with the line. Straight sweeps will clean these lines - looks HEAPS better..
It can take 3 - 20 hours to do a complete playfield, depending on the area you need to clean.