Building off some of the ideas from this question, we have single-animal human shapeshifters that put their clothing in Hammerspace (warning: TV Tropes) when they are in animal form. What exactly happens to their clothing I am not sure, but I don't want them to run around naked due to the sensibilities of my Earth audience.
Injuries sustained in either form transfer over, although mild lacerations of the skin can be sealed. Cuts that do not require stitches heal themselves (as you picture your skin whole and complete) and if you have, say, a broken bone with a single clean break, it will typically fuse back together. If you have a broken bone that hasn't been set, it will often fuse back together anyway and cause the shapeshifter lots of problems until it gets rebroken and set properly. Bones that have shattered take more magic and energy to fix than a single form transformation, as do bones that are in multiple pieces, missing, or significantly out of place. Missing limbs do not regrow unless your animal is a starfish or something that can regrow parts of itself naturally.
So say you are in your animal form and that it happens to be a coyote, for the purposes of an example. You get mud, blood, or some other foreign substance on yourself while in your animal form What happens to that mud when you shapeshift back into a human?
I'm looking for an answer that is easy, convenient, and maintains as much suspension of disbelief as possible. I'm spending a lot of time thinking about this, but I don't want my audience to.