Best ideas on how to treat fleas and mites?

Just wanted some ideas on what people use to treat fleas and mites? I got two hens off Craigslist and when I did my once over after getting home I noticed they have a few fleas and what I believe is mites. I use diatomaceous earth for my girls to prevent them but I’m not sure if it will work to get rid of them on these new hens? I also put Vaseline on their combs and waddles to try and kill the adults that were already attached to them.