Wet sanding question.

[rad]

Started wet sanding my '86 Champion 184 today. Started with 600 grit, didn,t seem to be getting any where. Dropped down to 500 grit,but still didn't seem to get anywhere. The gel coat is yellow in some areas, just dull in others. Should I drop down to 320 grit, or stay with the 500? How often should you change paper?

[rwainwright]

I have had to start with 220 before, just work your way back up, al lot of work but the shine will come back