Check out the caswell buffbook - it explains the key thing is surface ft per minute and gives you the calculations for rpm. You can also check out this chart >>
http://www.buffpolishgrind.com/techi...acefootage.htm
Assuming you are using 4 in" wheel then you are looking for something between 4000 and 7000 rpm. In other words your polishing wheel is currently going too fast and is unlikely to have enough power so when you apply the compound you can't apply enough pressure to melt the compound without the wheel stopping.
Alternatively maybe try 1 or 2" polishing wheel which will have the benefit of getting into smaller spaces but it will longer to polish bigger areas as the surface area of the wheel touching the part is less. I have not tried this so I couldn't comment on how successfull this would be but maybe someone else who has tried this can help?