I use a Masking Tape ( art tape) to protect the areas from my paint.
At this point I'm using acrylics. I applied a sheet of paper and masked the lineart with the tape.
Because it's such a complex shape I could use Masking Fluid at this stage. ( works perfectly with washes and watercolor) and it's so easy to apply, using a damaged brush (that can only be used with this in the future.)