After cutting the facets, on the pavilion, with the 600 grit diamond lap. 
BEFORE redopping to cut the crown. 
Polish, do the last cuts first and back up to where you started.
The angles have to be brought back exactly to where they were cut at. 
This is where you use the cheater. Don't apply too much pressure or keep it
on the lap to long 5 to 8 seconds,(a heat build up could melt the dopping wax),
check and see what its doing, adjust cheater for side to side alignments, 
or height for heel or toe alignment. Note how the polish "line"
moves as you adjust these factors. You want the lap and facet to be parallel.

But first some theory.
Polishing is a bit of a mystery, you can polish with a compound that is softer than
the stone you are polishing, its not an abrasive process, its not a melting process.
Its more on the molecular-electro-chemical-atomic levels. To tell the truth Nobody knows!
Its a combination of these factors:
lap type, Lap speed (slower is better), Polishing compound, moisture of the compound.
type of moisturizing agent. Operator pressure of gem on the lap.
The masters of yesteryear used odd things like acids and urine, 
to produce attached oxides of the polishing compounds on the lap.
These methods were "trade secrets"

Patience is a major virtue. You need to consider each facet as an individual project.
Set your cheater on zero before you start.
Adjust to the exact angle, then polish for a count of 8 seconds, analyse--
Where is the polish line, bottom half, lower 1 notch, see if it moved up-
top half, raise 1 notch, see if it moves down.
Check the side polish line,  increase or decrease the cheater
5 notches--see the change. With a little practice you can hit perfect in 2 adjustments.
Next work on eliminating scratches. As soon as your satisfied, check it with a 10 power loupe.
Take out the rest of the scratches. Move to the next facet around the circle. 
Repeat till you finish the circle.
Move to the next angle, repeat the circle with the new settings.
When your absolutely satisfied with the pavilion.
Redop for the crown. Set up to cut the Crown. 
Store your polishing laps in sealed marked baggies.
FACET DOPPING
When you finish cutting the crown facets, 
CLEAN THE MACHINE, STONE ETC.
Repeat polishing proceedures.