I've said it before and I'll say it again. Compression pants. Put those on straight after the walk and for at least the first night after the event. It's not a miracle cure but will significantly alleviate muscle soreness the next day. Some people do use them on walks in cold conditions but so far my experience has been that they are too warm for that.
I think BOM do 3/4 length bamboo based fabric shorts - they might help and they won't be as warm as the compression pants.