Id never put boots or shoes in a dryer, thats just me. I have used a hair dryer before and will never do that again because the heat tends to make it smell worse.
I think a lot of it is water that is knda nasty that has dried in/on the boot/shoe.
Id get some non scented liquid soap that is leather safe and water and scrub them down then rinse, whipe down with a towl and let air dry..... That should take care of most of it. If the inside of the boot smeels then try some fabreeze.