I have an older car that I have been taking care of. However, One side looks good and the other is dull in shine. Should I clay bar the dull side or should I just fix it up with ultimate compound?
Clay bar it first and then UC. However before you do that...that condition (one side shiny one side dull) is kind of unusual, so let's stop and think about that. Has the car been parked its whole life with one side parked to the sun? Has the one side been repainted?
Go through your normal pre-polish regiment, wash, clay, then do a test spot and gauge the improvement. Use an orange then white pad to improve the gloss...