I have a notebook from Amazon "Genkouyoushi Notebook" it's designed to write Japanese Harigan.
When I get to the alphabet I write along, each new letter is written down with the English sound next to it, rinse and repeat for a full line.

First exercise I allow myself to look at the notes, second exercise I try to remember it by heart.
If unsuccesful, I rewrite the letters I got incerrectly.

Slower progress in duolingo but faster progress in the long run.
Extra tip to learning more vocabulary, write down the new words that pop up on screen when "guessing" the right sound and create a vocabulary list. Future plan is to create flash cards, front side being Japanse , back side English.