I never have house-broken a adult dog but I know alot about shy dogs. Helped my friend with a dog just like Brett(adorable name). Anyways, take Brett to your local park with Sam. Sam can help alot in this. Let children and adults pet him and socialize him. Always Supervised of course. Sam can show him how great it is to be around people. Let people pet her as well and maybe he'll follow suit. Good Luck and I hope I could help! ALso, congrats on the new dog!