I use the Coppertone Water Babies sunscreen on my white boxer. It's great because it comes in a lotion spray can which is so much easier than rubbing it all over his body. I also use same brand sunscreen stick for his face...around his ears, nose and lips. That way I don't spray the other lotion in his eyes. It works great on his sensitive skin!! I also just got a 3 pack of the baby sunscreen at BJ's for $10 so that will last me more than all summer!! Much more affordable than puppy specific sunscreen and just as safe and affective!
Good luck to your friend!