Sorry I didn't see your post until just now. Here is a link to where most of my stock work stickies are over at SRF. http://www.surplusrifleforum.com/viewforum.php?f=137
Shellac can be removed with Denatured Alcohol and 0000 steel wool. It will come off realy easy.
The Shellac on a refurbed Mosin is about the worst shellac finish I have ever seen. Ivan just sanded the stock, put a few stamps on it to say that it was finished and then I think they had a bunch of 4 year olds slap on the Shellac.
Some here will want you strung up for removing what is left of a piss poor finish that will only fall off on it's own in due time. Just remember that when you do strip the finish off your $69 refurb Mosin and apply a nice new Shellac finish, it will only be worth $60 to a collector. Now after you have it finished do not let Bubba see it because, he may try to get you to sell it to him for $100 to $150.
I will be the first to say that an oil finish is one of the best looking finishes that can be applied to a rifle stock and it is not hard to do, but you must take your time and not get in a rush.
Check out some of my stickies ( you can copy them and and give then to your friends if you like. :D) If you have any other questions, just ask.