I decided I wanted to make a frame by frame animation with a crayon look for the line art. So I am using the paint brush tool with a custom vector art. But when I start to draw Adobe animate begins to slow down and I'm unable to colour in the lines. Can anyone help?
You're better off doing something like that in Photoshop. Using a vector animation program to attempt to approximate a natural aesthetic is going to be problematic with significant trade offs in performance. You could attempt using the brush library to try and find a texture that suits the look you are after, but it is almost useless and it's very hard to get a line that looks good.