I am finally getting to my garage door, and wanted to thank you again for the suggestion of using Bondo auto body filler on the door!
I contacted the Bondo company (via internet), and their technician advised using the Bondo Auto Body Filler (not their product for rotten wood). So I purchased a large can from AutoZone.
I started scraping off the paint/rotted board over the weekend (bottom panel only), and Monday night my neighbor came over and I told him "my plan". Luckily, he is a generous young man, who 12 years ago, used Bondo on a vehicle. He had never heard of using it on rotting wood.
Last night he came over and we started applying the Bondo mixture. It seems to be working wonderfully. We have applied 2 thin coats, and, hopefully, will apply 2 more tonight (weather permitting). Then we will sand, and I'll prime. I am thinking of faux painting the entire door (something I got off the internet).
Thanks again for your suggestion.
Amer. 4L7 Mary