Not sure how you were advised to do the door with shellac first. Sounds like you have already done some prep on the door. Dipping is not great for a door but if needs must!!! The door will have come back a bit on the rough side so I am assumimg you have sanded and cleaned off the door.
First off, I would choose my stain, go for either spirit stain or water based stain and try a light coat first, I use an old cotton sheet to work the stain up the panels with an old half inch brush to help get it into the joints and mouldings.
Shellac dries very quick, but I have only used this in two quick coats, flatting between, before moving on to a coloured wax, which when dried was buffed up with brush and cloth to get a nice smooth aged patina, more so on getting doors looking like dark oak in old listed buildings.
You could probably leave out the shellac process and just apply clear varnish on your pine, matt or satin, thinned down for first couple of coats and leave it at that, job done!!
I don't like the water based stuff as it dries too quick but it still works, I tend to still use spirit varnish that dries over a couple of hours. Smells a bit if you do a job for a client and it does take time to dry. As a final finish, I have flatted down with a 240 grade paper then added a coat of clear wax and buffed to a nice shene. Lovely!!!