Coating boots with a water-resistant barrier such as silicon is the best preventative to wet boots. But even the best water-resistant material will eventually give way when exposed to enough water. If the water is only on the surface of the boots, allowing them to dry in front of a fan is normally sufficient. If your socks are wet when you pull the boot off, there is enough water or sweat in the interior for the boots to be put on a dryer.
Air movement is the key to drying boots. If too much heat is applied, it can over-dry the material, or take the natural oils away from leather. A homemade boot dryer accomplishes two purposes -- it keeps the boot open so that air can enter the entire inner area, and it encourages the air to flow in and out, removing the moisture. It is not necessary to remove all the moisture, just enough so the interior can dry on its own.
PVC pipe is easily shaped and cut to an appropriate size for boot dryers. It's inexpensive and doesn't require special tools. Cut two sections of a 1-inch pipe to match the length of your boot from the top to the sole, plus 2 inches. For example, if you drop a ruler into your boot and it measures 10 inches to the boot top, your pipes should be 12 inches long.
Drill about eight 1/4-inch holes in the top 6 inches of each pipe, and put a right-angle elbow joint on that end of each pipe. Take the lid of a heavy-duty 1-gallon plastic pail, and cut two 1-inch holes on opposite sides of the lid, about 1 inch away from the edge. Set the PVC pipes into the holes with 2 inches of the pipe projecting downward, and the end with the elbow joint facing upward. Secure the pipes with silicon glue.
Cut a hole about 2 inches from the bottom of the pail that matches in diameter the end of the nozzle of a hair dryer gun. Put the boots on the PCV pipes with the right-angle joint facing the toes. Place the hair dryer in the hole at the bottom of the bucket, and turn it on the lowest setting. Do not let the hair dyer run for more than five minutes at a time to avoid overextending it, and give it a minute break before using it again. Check how dry the boots are every time you shut off the hair dryer.