What is this? What do hot spots look like?

A hot spot is a patch of red weeping skin. They look as if someone had taken a sander to the dog and sanded right into the skin. They appear very quickly and can grow quickly. You can go to the vet for this, but I've successfully treated them many times with cornstarch. Clip away all the fur around the spot so it can air out well, pat the cornstarch on as thickly as you can. It mops up the wetness. Do that again several times a day, to absorb the wetness. Don't pull away the crust, just keep applying the cornstarch as long as more wetness appears. I believe it works by drying the spot. In a few days or a week, the crust will start to drop off on its own, the spot will start drying up, and then you can begin to pull it away but it's almost better to leave it to fall off naturally. If the dog really can't leave it alone, you might have to use an Elizabethan collar for a few days.

They start looking quite red and bloody and the fur feels gunky.

They then ooze a yellow gunk with a very distinctive smell. What you are after doing is drying it up and preventing it from infecting.

I use all sorts of things such as salt water, hibiscrub, iodine, sudacrem and any other remedy that people find. I don't know if peroxide stings, never used that. However in reality they usually take the same time to heal and dry. Also clip all the fur away, and definitely stop her from chewing it.

Once they do dry then the scab falls off in bits.