If the buffing doesn't improve the end result by over 98%, ask him on pickup to complete the receipt to acceptable ATO standard with full price, letterhead etc.
Also take along a well dressed friend in pin stripes to take Pics of your car, its crummy paint job and the workshop's signage. As he/she is standing kerbside, point out to the owner that person as a 'clerk from a law firm' and that he'll hear from them if he doesn't give you a refund.
Let's call this 'sabre rattling' if required.
'Sabre Rattling' has worked before.