I changed my way of working to lay down some fur strokes then cover with a wash of a warm grey, add some more darks and then do another wash.
I am using acrylic artists ink for the black because I can then soften it with coloured pencil.
I reserved the paper with white pencil, I used a wax based pencil as it will be easier to remove when I want to reveal the paper, there will be a lot of finger crossing at that stage. Of course it would have been easier to use masking fluid but mine is several years old and looked like it could have got out the bottle itself.
I have done about 3 layers up to now, there is more cat but I wanted to see if i could make it work before I got too ambitious.
I do think watercolour is easier to work with in small areas as it doesn't dry as quickly, but it remains to be seen which I will end up using for larger works.