What do you mean by inconsistent? Is it too thick at some place and thin at others? I used shellac on my most recent speakers, and it is a very easy finish to work with. You can always touchup by just applying it again on top. The top coat dissolves the layer underneath, and thus very easy to fix any errors.
I had bad results with brush... so i just made a cotton pad, and rubbed in the shellac (kinda like french polishing). I got pretty good consistent results.