Welly scrapers

If you're at all handy, you can simply take a length of dull edged metal and slip it into slots made in 2 hunks of wood that sit at either end.

I was at a garden show and saw a metal 'dachshund' that was actually a bootscraper that now sits on my back porch for scraping off my wellies. You could always call local garden places and ask if they have any.

Or you could always buy online something like THIS.

They'll do a pretty good job provided you scrape off the mud while it's still soft rather than dried out. If the mud has dried up, I simply stand on the porch, boots in hand, and bang the soles together and mud crumbles off.

My personal favourite is the metal boot scraper.