I keep a large sponge with me so I can wipe my boat down after every trip. Even when there doesn't seem to be much in the water, I still find a thin line of scum on the hull so I wipe it down while it's still wet. Makes the work a lot lighter and also prevents me from bringing any "nasties" with me to another body of water.
I always carry one of those big dog-bone shaped sponges stuffed in my bailer. A word of caution, post-trip that becomes a dedicated canoe sponge, now embedded with sand and grit. Hide it with the canoe gear and do not allow your teenage son to wash your car with it.
The scum line is much easier to wipe off when it is still moist sludge, but it is the crud in the canoe that gets me. Or gets on me.
Before flipping the boat to drain the bilgewater I wipe up the worst of the sand or mud or loon crap inside the boat. I don’t want to flip the hull and have the bilge water wash that crap into the gunwale and thwart crevices, but I really don’t what to hoist the canoe onto the roof racks and be showered with sand or feel a big glob of mud fall atop on my head.
I really need to hurry less at the take out. Oh hell, I’ve left the truck windows down to cool off the cab and dumped bilge water on my seat. Who hasn’t?
A big ole glob of mud isn’t pretty when it’s dripping on the truck cap, less so when it’s running down the back of my neck. Yeah, lesson learned more than once. Duh.
Still, mud in the hair is better than tar. I paddled under a low headroom bridge. Lots of tar stalactites dripping from the underside. I zigged when I should have zagged. I shoulda worn a hat. Could, shoulda, woulda.
A friend cut the tar out of my hair. With a pair of Swiss Army knife scissors. Unless you are going for “Escaped mental patient” that is not a good look.