Copy these into a Folder on your dropbox and import them into a new set of Procreate brushes to add instant shape tool functionality to Procreate.
They are pretty simple... they simply stamp the shape at the point you tap, in whatever color, size and opacity you have selected... do this on a new layer, and use the transform tool to adjust aspect ratio... or to get a larger size than the maximum size that the brush will draw.
It is easy to add more custom shape brushes... just create a simple, square, white on black image of the shape you need and copy it to your photos or dropbox... then- duplicate one of these brushes and under Sources in brush settings, import the new shape graphic you created.
The Straight line tool uses a different approach... the graphic is in the grain source. This results in a brush that, at 29% size will draw a straight horizontal line in either portrait or landscape orientation, just about anywhere you swipe your finger ( approximately- again, do so on its own layer and use transform to position accurately)
Or, swipe your finger all over the screen to create ruled lines with spacing controlled by the size slider.
Another thing you can try is to duplicate these brushes and try changing the Grain graphic... you generally want a grain pattern that fills the entire graphic, like the built in paper or canvas textures you can pick in the Source>Grain dialog.
This will create different effects.
ANother trick, for those who want a more dynamic brush-like feel is to use the outline shapes as a Tracing Guideline.
i.e. Stamp the shape on one layer, then create a layer over that and hand-draw over the shape using the brush you prefer.