How to create spray paint effect on a curved line. (A bit like fountain fill but not fountain fill)

Not sure how to describe this so probably best to do it with pictures.

I have this...

and I want to add the blue spray paint effect to make it look like this...

In other words, how do I add the Blue Bits? I assume I will need to create them in Photo Paint with a spray effect of some sort or with some sort of fade or fountain fill in Draw. I've no idea how to do that either as a transparency or on a curved 'line'. Any advice or links to how-to's greatly accepted.    Chris

(I had an artist design this for me and she gave it to me as a.psd file and now I want to add the Blue Bits to my vector.)