Wonderful time-out painting, dear Sandra!
As for Your question You posed, there are at least three possible approaches You may test (the simplest ones perhaps, without making recourse to particular sheets or stickers).
- try with enough metal content;
- try with either the roller at adequate pressure and thinned enough or very low pressure chalk on the painting and a low presure smoothin with either the first or the last blender type (not too much pressure)
- use lower loaded watercolour with very short strokes in the right direction (less controllable)
Let us know in case...
Panta rei (everything flows)!