while you have propley all seen a pro mototcross rider cleaning there bootss with a pressure washer i dont reckomend to do the same because the leather falls apart after awhile of doing this.

step1: if you have been riding in muddy conditions,give your boots a light hose to get off any big chunks of mud

step2:get a bucket of warm soapy water and scrubing brush and sponge

step3:use brush pr sponge or both to give you boots a good wash

setp4:put boots in derect sun light let them dry and there ready to go again

tyre cleaner works a treat on leather boots.

Try getting a toothbrush and some turps for stubborn stains.