I used Sedalin for years and years with Chloe, worked well. She had such bad feather mites and mud fever scabs vet let me have some as it was only way I could get near her to do them without getting kicked or stamped on. One time I used Domesedan, wow, now that really knocked her out. Was good, really good, and I would use again (with caution) because she was rather wobbly and we did her in our garage lol so I was glad when she "came round" and it wore off somewhat. From memory, I would administer the Sedalin about half an hour to an hour before proceeding. I think it was closer to an hour to make her dopey now I remember. I guess its different for every horse though?