opps- another door bites the dust.. lol.
As far as muddy paws, when he settles in, trim the hair on the bottom of the paws. That will really reduce how much he brings in from the outside. Also cheap bathroom rugs- the thick pile kind- are excellent to clean big feet. I have then at the entry door they do in and out of..
It may also take a few days before he stops looking for his owner. Saints are known for being very loyal, and it may take a while for him to get over this. Removing also any blankets etc the other owner gave will help. As long as he smells these, he may continue to look for his old owner.