the two basic ways of polishing are :
Oil on first . all over , as thin an oil as possible , never a boiled oil or a drying oil , then wiped off but not scrubbed off .
Vegetable oil OK , doesn't matter , but thin mineral oil is much better .
In this process there is no shellac used , no wash coat , no other gum or resin , they would be just an impediment .
Spirit , oil , and pumice , linen for rubber cover or raw coton rubber without cover are the materials . Cotton cloth is useless .
When the wood is filled , only then is shellac used , bit by bit , and pumice is abandoned and not used .
If a heavy coat of lac is desired , pumice may be used to smooth it out , but if so , it is done with a spirit rubber , without any shellac .
If this is mastered it produces a fine finish . It is very difficult to use on spruce or cedar.
It is very fast and a guitar can be polished up in less than a day .
It takes time to harden up . It is rare to find anyone who uses it but was common in the antiques trade .
I have used it on guitars .
No oil , only shellac . Padded on , sprayed on , brushed on , whatever . Then polished out in the end . There are a lot of varieties of process .
Oil not used untill there is enough lac to prevent oil getting to the wood .
In any case oil should me spread as soon as it is applied to prevent it going through in a spot . Especially if the finish is thin .
But if oil does get in the wood and make a splotch in an otherwise shellacked finish there is only one remedy . Remove the finish .
A pain but that s how it is .
I always found acetone pretty good at washing oil out .