Make sure the belt is routed properly. There's usually a diagram somewhere under the hood- - - - -if one of the heavy load pulleys like the crankshaft pulley, alternator, or the A/C compressor doesn't have enough of the belt wrapped around it, it will squeal. Since it's only happening after startup, pay particular attention to the alternator. Recharging the battery after startup puts a lot of load onto a very small pulley.
Jerry
These are your first steps. How is the tension on your tensioner? Belt dressing is not meant for serpentine belts. Make sure your buddy degreases all the pulleys before he installs a new belt so you don't get contamination on that one too.
