I use simple green and denat alcohol mix too. Spray on, let soak, scrub with toothbrush if needed, hose off with mix again, compressed air to blow dry.
I buy the denat alcohol they sell in paint depts. My current can is S-L-X denat Alcohol. Wasn't aware there were differences, but maybe its the additives that make it unsafe to drink (poison)?? Not sure than would make a diff in cleaning action though.
Try the cheapest?