Hi,
You need to make up a polishing pad with a cotton filling and a very fine-woven cotton outer cover. I polish furniture regularly (I mean wipe on shellac; that's polishing) and make up a new pad for each day, because they dry out and a fresh clean pad works better anyway.

A cotton sock (like an ankle/sneaker sock; clean, please) is a good filler. This is rolled into a ball and then wrapped tightly with the cotton cover (like wrapping a burrito)/ Keep the cut edges of the cover wrapped inward so there are no exposed thready edges. I use old soft 100% cotton sheets, torn into rectangles about 12x14.

Wet the filler with alcohol and squeeze out excess. Quickly wrap the cover on as described. Form into a ball with a completely smooth face with no creases in the pad or cover. Creases leave streaks of finish.

I keep an open container of shellac close by, and work with a 2" bristle brush in one hand and the pad in the other. I use the brush to apply small amounts of shellac to the pad. The Sealcoat is a 2lb. cut and requires no further dilution. Keep the filler damp with alcohol by replenishing it from time to time. Striking the pad into the palm of your hand will bring a little more alcohol to the surface in between refills. This is needed because you're diluting the shellac while it's in the pad.

I always start with two coats brushed on and allowed to dry at least half a day, or until hard. Then, sand with a 220 grit sponge, taking care not to burn through corners; you just want to get rid of any fuzz, drips, ect. You will perfect it later with the padding-on.

Work with the grain, develop a technique where the shellac is applied evenly with no excess at the edge of the stroke. Excess finish will fail to dry instantly; that is the point of this exercise, to put down only in layers only a few molecules thick, so the solvent alcohol is evaporating instantly, and you can wipe it out 100 times before quitting for the day. Work from both ends. This means don't always work "off" one end of the piece, Reverse it (or stand at the other end) and wipe in the opposite direction. Sometimes it's tempting to want to work across the grain. This will fill in the finish very effectively, but will require many more strokes along the grain (or a 1000-grit wet sanding) to hide the cross-grain marks. Wet sanding BTW, is perfectly fine on shellac, and with care you can flatten out any mistakes and get a finish of 100% reflectivity.

The brush comes in handy for getting finish into corners, moldings, and turnings. Follow the brush immediately with the pad to smooth it out. I mean brush in one hand followed inches behind by the pad in the other hand. Do not go back until it has dried if you have too wet a coat on the moldings.

You will never get the inside corners of panels as smooth as the flattest areas, so these will inevitably need to be rubbed out with fine abrasive, then polished one last time for uniformity.
Hope this made some sense. It is a fantastic technique to master, the results are very pleasing. This is the gateway to French Polishing.

Casey

The seal coat is basically a clear shellac, but it is usually applied before staining to minimize blotching.

Why would you need to seal the stain?