A projector would be nice! I use tracing paper. I trace the sketch, then using carbon pencil I rub the BACK of the tracing paper, whereever there are drawing lines. (do not have to blacken the whole back).
Then I take the tracing paper with carbon back and position it on the watercolor paper, tape it down and REtrace the drawing , pressing hard so that it pushes the carbon onto the watercolor paper.
Sometimes, I sketch right onthe watercolorpaper and use a F pencil for finer line. It erases right out without damaging the paper at all.
I would love to see some of your work. I have two new things posted on my "Equines in ink, the artists journal" thread.