I know a guy who does a lot of timber based work (furniture, small sculpture etc) and sought his advice on finishing a kit. He said if it were him he would use white shellac instead of a grain filler, so that it formed a nice even base to lay the stain down on. This goes against almost everything I've seen on this forum.

Wouldn't a shellacked surface prevent the stain from soaking into the wood?
Even if the stain dried nicely on top, would the shellac affect it's colour?
I've no idea of the cost involved - would it make the whole thing more expensive?