[Paul JD]

With a small part like that abrasive paper and a bit of elbow grease would probably do the job as well as anything, start with a coarse grade to cut through the old paint and then use finer grades to get a nice flat surface to paint. Failing that you could use paint stripper (although with modern health and safety regs a lot of consumer grade paint strippers are not very effective - not like the old Nitromors that worked in seconds!) or depending on what type of paint it is cellulose thinners or acetone might remove it.