First question, are the dragons housed together? If so, seperate them immediately so they aren't both contaminated.
Dealt with coccidia with one of my dragons and it isn't a fun experience. I would suggest switching the substrate to paper towels so you can throw it away whenever the dragon defecates. The only cleaning products/tools that kill coccidia are steam cleaners or the pink sanitizer from bd.co as far as I'm aware so every time your dragon poops in the enclosure you want to throw away the substrate and even blast the area with a steam cleaner or use the sanitizer as instructed. You should also remove any porous directions from the tank and keep it minimal until after the medication is done. I know some people who used cardboard boxes as temporary basking spots and changed them every day during treatment.
To not cross-contaminate, I wouldn't let your dragons free roam in the same area until they both test clean.
Let me know if you have additional questions!