Scrub daily with salt watee and i pack crevices with red horse field paste overnight as stabled and get poo and wee on feet at night. I also salt scrub every few days. I dont use any strong chemicals as this can cause damage to healthy tissue as well. I know copper sulfate is very effective but i usually find salt water scrubs do the trick if you treat aggressively.
If it is just normal thrush, I use canesten thrush cream from the chemist, or a similar cheaper make. 1% My horse had a deep hole in the frog/heel and I had to mix that with a special cream as it was really quite bad. It worked a treat. Had it originally for the first 6 yrs I had her, and had spent loads on different boots, bandages, creams and potions, and nothing worked. She's not had an issue for the last few years.