For front guards, if you want to do it right, get one that rotates with the fork. Bender Fender is ace, but small, if you want more serious mudstopping then something like a Shockboard (the mounting hardware is crap but add a couple of cableties and you have something light, not too ugly, and hugely effective). Front crudcatcher/similiar are just a joke really, both ugly and ineffective.
Rear… Some bikes struggle, on a full suss they tend to have to be so high that they’re not very effective. Crudcatcher used to be the daddy but the current design is a total abortion of a thing, such a step back (but fixable- with a soldering iron and a lathe and a proper bolt, they work very well indeed)