My speciality is mudflaps. Yes, I am the Mudflap Meister. Actually, splashguards is a more apt descriptor. This is because I have never seen fenders that are long enough to keep the bike guts clean (1st priority), the pilot's feet clean (2nd priority), the pilot's buddy-who-is-drafting, from spitting out road grime (priority debatable). The only exceptions I have seen are a couple of antique bikes.
What follows is only to be attempted if you have a high tolerance for looking like a dork. Since many bike riders look like dorks to many non-bike riders, I feel I can blend in sufficiently so as to become somewhat anonamous. Nevertheless, be fully prepared to have rocks thrown at you by your buds. People will think you are being housed in a facility that lets it's residents' out for limited errands.
I riveted on some carefully crafted stair tread and these puppies work
. Ya don't get no betah! Cool? Nope. Long? Oh yeah - wide as yer aunt Bertha's butt, too. The front starts all the way up the fender at the 10 o'clock and comes down to about two inches off the ground. It's the only way, brother, otherwise the wind will whip the goo back at you from around the sides before it hits the ground. The rear flap starts three inches up the fender and ends at about the 8 o'clock position. Your 'roostertail' should be no higher than two feet at that point. Your buddy behind you will appreciate that fact - but then, you'll have no buddy behind you, or anywhere near you.
Road grit and grime are now minimal. My shoes are clean. Wet? Sure, but it cames from the sky, not the street - it's different.
Keeping Panniers Clean: There is no way short of full skirts that you can stop all the side spray from the tires. Learn to sew or have waterproof over-bags sewn for you. They might be available commercially. My wife made me a set for my cheapo panniers for pennies on the dollar. The Topeak handlebar bags come with a cover that gave me the idea.
Thus Speaketh The Mudflap Meister.