When I use shellac on my saw handles I apply a total of 6 coats. The 1st coat is sanded back to 150g. The 2nd coat to 220g. The 3rd coat to 400g. By that stage I expect most of the grain should be filled within the wood surface. The flat faces of the handle are always sanded over a glass surface. The time delay between each coat is minimal.
The last 3 coats of shellac are to add depth over the wood surface. Each is given 24 hrs between coat. Each coat is lightly abrading with a very fine grade sanding pad before the next coat is applied. After the last coat the shellac surface is then left for 5 days to harden.
The shellac surface is then lightly rubbed back with a cut and polish paste that's hand buffed to a shine. To achieve a greater shine, the surface is buffed again using a power mop fitted to a pedestal drill. (no cut and polish paste used) This step is again repeated 30 min later. Job done.
Stewie;