How to create and convert Photoshop custom shapes into brushes tutorial
Create a new document, select the CSH tool and set to pixel fill or layer and then apply the preset with the required size, color etc. Re-apply to build up an interesting stroke design. Use the edit menu define command to create a new brush from the generated artwork. Select one of the paint tools in the toolbar and then Paint.
1) Select CSH tool in the toolbar
2) Set to layer or fill pixel option (top bar)
3) Apply shape (or re-apply shape and create more shape decorative graphics)
4) use visual effects or change blending mode or change shape and re-apply as required
5) edit menu and define brushes
6) Saved to preset panel
7) Select a stroke tool as required and paint
If you want a direct translation of the shape to a brush, the best option is to use the shape layer and apply a single shape in black (filling the entire document). Flatten the image and then use the define command found in the edit menu. You can, as the presets are vectors, apply them to any size of document (say 2500 x 2500) and then define that. Sadly there is no tool that can migrate a preset from one type to another.
You can also apply a shape with layer effects or use visual effects such as blur and then define that as a stroke via the edit menu "define brush" command. You can also set up an action to repeat this action with any preset. It is a quick and easy way to create endless tools with the presets as a great source. The image below combines multiple blurs along with the wonderful oil paint filter
You can use the presets as a source for patterns and then use the patterns as the source for the strokes instead of the vector. You can also use the shape in the 3D menu with the new extrusion from layer command. Below you can see the same artwork used as a 3D model and then used as a source for a new stroke and added in orange
Other tutorials for Photoshop custom shapes include how to use the Photoshop shapes with the creative cloud libraries and how to split shapes and use fragments of paths in Photoshop and how to draw irregular shapes with Photoshop tools tutorial
You can also combine gradients with the custom shapes to create even more amazing brushes and there are a number of tutorials on the gradients such as how to install the Photoshop gradients and how to use Photoshop gradients across channels