u could also just do this with a brush that has color jitter, but what i like about using layer masks for highlight/shading layers is how simple and reversible it makes everything. i can use whatever brushes i want, and erasing/redoing things is super low stakes, which is great when i often approach this stuff with a super trial-and-error approach.

example: have u ever thrown a gradient w multiple colors over an entire piece, set it to multiply etc, and then tried to erase it away to carve out shadows/highlights? it's super frustrating, bc it looks really good, but if u erase something and then change ur mind later, u basically would have to like. recreate the gradient in the area u want to cover up again. that's how i used to do things before figuring out layer masks!! but masking basically creates a version of this with INFINITE undo bc u can erase/re-place the base layer whenever u want.

anyway, back to rambling about this specific method:

i actually have TWO of these layers on this piece (one with the liquified swirls shown above, and another that's just a normal concentric circle gradient with much broader stripes) so i can vary the highlights easily as needed.

since i've basically hidden the rainbow pattern from myself, the colors in each brushstroke i make will kind of be a surprise, which isn't always great -- but easily fixable! for example, if i carve out a highlight and it turns out the rainbow pattern in that area is way too stripey, i can just switch from editing the mask to editing the main layer and blur that spot a bit.

u could also just do this with a brush that has color jitter, but what i like about using layer masks for highlight/shading layers is how simple and reversible it makes everything. i can use whatever brushes i want, and erasing/redoing things is super low stakes, which is great when i often approach this stuff with a super trial-and-error approach.

example: have u ever thrown a gradient w multiple colors over an entire piece, set it to multiply etc, and then tried to erase it away to carve out shadows/highlights? it's super frustrating, bc it looks really good, but if u erase something and then change ur mind later, u basically would have to like. recreate the gradient in the area u want to cover up again. that's how i used to do things before figuring out layer masks!! but masking basically creates a version of this with INFINITE undo bc u can erase/re-place the base layer whenever u want.

anyway, back to rambling about this specific method:

i actually have TWO of these layers on this piece (one with the liquified swirls shown above, and another that's just a normal concentric circle gradient with much broader stripes) so i can vary the highlights easily as needed.

since i've basically hidden the rainbow pattern from myself, the colors in each brushstroke i make will kind of be a surprise, which isn't always great -- but easily fixable! for example, if i carve out a highlight and it turns out the rainbow pattern in that area is way too stripey, i can just switch from editing the mask to editing the main layer and blur that spot a bit.