My rat scratches his face and has sores.
What's he got? Mites?

The majority of the time it is _NOT_ mites. Scabs are more likely to be caused by too much protein in the diet, allergy, or skin infection. Mites are only a possible cause.
If it is mites. Tom found Ivermectin (0.02 mL of 1% oral solution/lb, diluted with water to 0.1mL doses) best (MJC). This is available for horses at feed stores at about $44/25mL (2500 doses). Any vet can dispense less. Try to get vet to give you a vial with undiluted 1% and a syringe, and dilute and dispense yourself. Diluted Ivermectin will curdle. Treat all rats that could have come in contact. Clean and disinfect cages. Repeat if nec. at 1 week.
I have found that Zimecterin (horse wormer) works well. Take a little dab about the size that fits neatly on the flat part of a flat toothpick and smear it on the rats tongue. Repeat in 7-10 days. If you must use sprays, use the kind used on parakeets, such as 10 in one.