Just an example:




I test the round brush from my own scratch

but three color also, if you want to change the color with this brush.
Layer > New Correction Layer > Hue/Saturation/Luminosity

here go there, so you could to paint or draw the line no matters! also, I forget another thing, maybe this one! how do you think? if you feel interest to make discover new experiment? so there!
Layer Property > Border Effect > Watercolor Edge

See? Kinda see close to 3D brush then to make bright color? you can.
Layer > New Correction Layer > Hue/Saturation/Luminosity > Luminosity 80% or whatever what do you want > Blending Mode > Add (Glow) with Layer Property > Border Effect > Watercolor Edge

I feel do needs to more have few experiment to make create.
Enjoy It
I don't like to having more detail by CSP says, lacking of the information.