If you are in Innsbruck take the bus to Reutte/Tirol, then another bus to Weissenbach
Via Kempten (Germany) to Reutte/Tirol: take the train and from Reutte the bus to Weissenbach
Via München-Garmisch (Germany) to Reutte/Tirol: take the train and from Reutte the bus to Weissenbach