What are some suggestions for teaching my 13 month old to be nice to his new baby brother?

My baby was born on Wednesday and we brought him home on Friday. Our older two boys ages 3 1/2 and 13 months stayed with their grandparents in a hotel until yesterday. Now they are home and really excited about their brother. However, they really aren't sure what to do with him. The oldest knows a little better and is a lot better with him but our little one is a little extra rough. I am working on showing him nice touches but I was wondering if anyone else had a good suggestion that worked with their older baby to ease the stress over it. Currently he tries to pat the baby everywhere, but because he's so big it comes out more of a hit than a pat. I put my hand on his and say gentle or soft and help him rub the baby instead of pat.