As previously mentioned, I to cut up plastic and tape it to the floor boards.
The last time I ran my car was in 2011, and I am working on it as we speak. Today I climb out from the inside and lo and behold there is a clump of salt on the garage floor. How did that get there?
I did try the sprinkler, that works good! Then I also strip down to my swimming shorts, lay under the car with a nozzle on my garden hose and wash as much as I can off.
Mud flaps are great as well, and don't forget about trailer mud flaps.
The other thing I do is clean the vehicles/trailer, etc before you go to the salt, get mud off etc.
Also in 2011, we tried using two vehicles. One to go back and fourth the hotel, one for towing/pushing the car. IMHO not worth it, two vehicles to clean, uuughhhh
TIA
Clay