I never, ever EVER use the Brush!
Picture White Van Man scrubbing the f%#k out of his back door where he or a WVM colleague have etched 'I WISH MY WIFE WAS AS DIRTY AS THIS VAN' into the 3000 mile, M25 tar-encrusted paint. After use, the Brush is usually tossed into the crunchy, oily brine that lies around the Jet Wash stand.
Never mind leaving swirl marks, the Petrol Station Jet Wash brush carries so much grit, sand and crud it can only spell disaster for paintwork.
Avoid at all costs!