on the guide, draw a series of squished circles slightly overlapping.
using an eraser that is about 2-3 pixels smaller than your drawing brush, erase half the inner circle alternating sides as you go down the line.
then erase the rest of the inner circles the same way, but in smaller sections.
adjust the size of the eraser depending on how thick you want the inner lines.
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i hope this helps and i hope it's easy to understand! using chain brushes can be helpful, but they sometimes look too stiff, so i find doing it this way can look more fluid
Edit: I'm just using a basic round brush with min size up to 100% brush size varies depending on canvas size
Watching oomfs move to tumblr because it's much better catered for content creation and easier to filter out unsavoury niggas in communities you browse mhm yawp yawp