How to "Gloss Up" Shellac!
To "polish up" the Shellac, you will need to order Rottenstone, if your looking to gloss up the Shellac. you must also, allow the shellac to cure out for at least 72 hours before rubbing, the longer the better it will rub or polish up.
Also, you should use water with either the tripoli or the rottenstone as a lubricate.
Rubbing and Polishing powders
From my knowledge, they are 3 different powders, as was already mentioned and Tripoli is the finest of the polishing powders, it is white in colour.
Pumice, comes in four grades, the 4 FFFF being the finiest of the 4, then comes the Rottenstone, which is a greyish colour powder that is used to really polish up the coatings.
I have heard others mention that Tripoli as being the same as either Pumice or Rottenstone. it maybe that way in some countries. I know if you order Tripoli you may end up getting Rottenstone.
I use the FFF Pumice for my low rubbed out finishes, If I am going for a high gloss sheen I just continue on using the Rottenstone for my super high gloss finishes.