Kelley Jones’ Batman

I wanted to paint a super hero as a present for my (first) godson’s 14 year-old birthday. He was going to get a real present, of course (grin). I went with a dark and pointy version of Batman by Kelley Jones, reminiscent of a genie out of a bottle.
I wanted to paint the black around him. I started with pencil sketching on a thick watercolor paper:
pencil sketch on a thick watercolor paper of a Batman with very sharp angles and standing on a sort of cloud
Then I used masking fluid. This time I did not add any water. It had been painstakingly long and tedious to peel it off the last time I tried this. And given the thin white lines I was aiming for, I didn’t use a brush, but … a toothpick. After a loooong time I was done and I framed the painting with masking tape:

I prepared a wash of lamp black and stroked with a synthetic and quite large flat brush. It was barely grey, so while the paper was still wet I added pure black, and another time , and another time. After the paper had dried, I peeled off the gum. It took me an hour. Tedious and painstaking again. I have no idea what I am doing wrong, and it’s possible the fluid I have is too old (I’ve had it for twenty years), or it’s my Hannemühle paper that isn’t right, but clearly this isn’t supposed to be so hard. Anyway, here goes the result:
Black paint applied all over. Masking fluid peeled off. Signature and date added in white at the bottom right. The Masking tape is still in place.
And here is the final result once fitted in its 20×30 cm frame: