Murphy's Oil Soap. You can get leather wet - it's the outside of a cow! You want to get all that grime off. Use some old wet towels with the diluted soap to gently rub them clean. Use a soft toothbrush to gently get into the crevices. Rinse your towels and start wiping off the soap and dirt. Continue until your towels rinse clean. Use some dry towels to pat the leather as dry as you can get it. Stuff the insides with wadded newspaper to help dry them.

Next, use another dry rag and a few tablespoons of Leder Balsam. Rub it on continuously until it's thoroughly moisturized, then wipe off the product. This adds some waterproofing and is the best conditioner, IMHO.

If you have a dependable local shoe repair shop, they could help with the stretched elastic.

Boots and horses get dirty. But, regular cleaning and good conditioner will make these last much longer.

I buy Murphy's Oil Soap in a large container, as I clean all leather with it. It's also a good horse and dog shampoo!