Even with Photoshop, pencil is difficult to clean up. Use the pen. Try wider nib black and grays to fill in. Try a lettering guide to make your letters equal height and aid in line spacing. Pick one up at arts/crafts/drafting stores. Looks, something, like this:
_____________________________________
! _____________________________ !
! (_____________________________) !
! _____________________________ !
! ( ) !
! (_____________________________) !
! _____________________________ !
! ( ) !
! ( ) !
! (_____________________________) !
!_____________________________________!
for, say, 1/4", 3/8" and 1/2" letters. It's plastic.
Good job!!
THAT didn't work. Oh well, back to the drawing board!!