I just had a professional exterminator come to the house for the same problem. He uses a copper mesh to plug holes. Steel wool rusts.
I also am employing a trick previously reported on this forum. Put aluminum foil under the tires. They cannot get sufficient traction to climb the tires that way. I am hopefully taking that theory to the next level this year. I am parking the MH on aluminum flashing with car wax on it to make it even slicker. The flashing should be permanent, and I can tape it to the MH garage floor and always park in the same place and hopefully have all year protection. I will report on results next year.
I forgot to mention the pro also told me to use fox urine available at hunting supply stores to deter entry. I will place a few drops on the afore mentioned parking pads.
I will not use poisions because we have pets. My father lost his dog that way. Apparently the critters carried small bits to a area accessable to the pet before they expired. The dog got into it and also expired. Very traumatic for all involved.