Right, I think I’ve done it! I’ve created my own brush!
So tap the brush tool on the right, then tap the square box at the top and choose Add Category. It will call it Brushes but if you go back and choose Rename Category you can call it what you like. Now select New Round Brush.
View attachment 104770
Under General, these were my settings. I wanted to start with a fairly thin brush so the size is quite small and I also made a fat one later.
View attachment 104768
Under Dynamics I choose this:
View attachment 104769
The size which I have set to 49% gives it a slight taper at the start and finish. I made a small one with a taper and a fat one without - see image below.
There should be no images in the texture section.
Once you have set this,
make sure that the paint brush at the bottom with the drip is unselected.
View attachment 104771
Hope this works for you!