Don't worry about being off of the spine. Most people on the rodboard (www.rodbuilding.org) think the spine issue is overplayed. It is likely that you will never notice the difference. I would go ahead and align you guides to the seat. Relax as this will in no way ruin your rod (trust me I know the feeling of painc well).

I have reused brushes with success. When I am done applying the epoxy I soak the brush in denatured alcohol for a bit. Next I squeeze out the epoxy and solvent in a paper towel followed by washing the brush in warm soap and water. Hope this helps. You are going to love your rod! Beware, you have now entered into the hopeless addiction of rod building!

Peter