Skin Problems Skin Problem and Nails

So I know that my guinea pig has mites so there is Ivermectin coming through the mail and it will be here within a few days, but today my guinea pig actually has a blood spot, which I believe is from her itching. So I am wondering, is the blood spot ok and it will go away once the medicine gets here or is there something I should do right away? I also need to trim my guinea piggies nails and I can do it, but they always seem to bleed at least once and they twitch a lot when I try to clip their nails so are there any easy ways to clip their nails? Also, my guinea pigs nails are a bit longer than they should be but I can't just clip through the blood part of their toes, so will the blood in their nails retreat slowly when I clip the nails shorter?