I think the shapes you are working with will not lend themselves well to stroke practicing, only the slashy ones and the ampersand.
Try making a pounce pattern and practicing on an old fridge, a toolbox, even a junk fender from the salvage yard.
I never did the slash/shape/speedball thing.
Started out drawing my letters and then filling them in, eventually I just had to draw the simplest ghosts of letters or even the uprights. If you learn how to build a basic letter, as an A, B, K, M, O, R, S, V, you can use that to build any other letter right in your head as you go.
Use a ruler for the top and bottom lines, remember the center line is usually a bit higher than center. Round letters are bigger than the top and bottom lines.
I started with thick and thin, like a roman or an optima/percepta, then worked my way to straight sans serif stuff.
Love....Jill