Drum squeal on new brakes is most common from two scenarios. Either the brake shoe material is too hard, or the new shoes haven't bedded properly yet. I tend to agree with the tech that mentioned to use the brakes more. It takes a few hundred miles of city-type driving to get them to seat properly. Especially on larger drums like yours.
Every day's a learning experience, though sometimes not what we expected.
2012 Jay Flight 19RD
2016 Ford F150 XLT 2X4 SC 3.5L Eco Max Tow
2010 Tundra TRD DBL Cab (Traded)
2 new fluffy Corgis, Bayley and Stanley