As you reach ketosis a coated tongue is normal. I also brushed my tongue during my fast, I used a little plastic tool thats used for scraping off lottery tickets, lol. Latinmess used a dull butter knife to scrape hers. I have heard of a tongue scraper, maybe you could find one in a drug store but really anything dull will do the trick.
Scraping the tongue before brushing really helps but the coating always comes back and bad breath is part of the process too.