This is a sketch from a picture book I am working on.
I was happy with it, so scanned and printed it onto my final WC paper. My on-line critique group thought the tail on the left bird looked odd. I agreed, but reluctantly.
I was resigned to losing a bit of time and starting over until . . .
I remembered my magic jar!
Daniel Smith Watercolor Ground.
I got out my magic brush and covered the tail with a few coats. It blended nicely into the paper. You can still see a slight shadow, but it lightened it enough. After it dries, it takes the watercolor washes nicely. It can be used on just about any surface

Here is a closer image.

And a shot of my drawing table showing my process.
I have started the washes in the sky, and it really worked . . . like magic.
Thanks critique group and Daniel Smith!
It should be finished soon.