Well I had one of those too lol - awful isn't it. I kept her toothbrush (well several of them) with mine. SO that when I cleaned my teeth, I would remember too.
She got to pick which one she had and I used another one.'I would sing, let her brush my teeth, prop her up against the mirror and let her have a go at copying me....one never worked two days in a row, so whatever it took that day.