Jack of All Trades, Master of...All Trades

Unlock and equip Warfarer, the do-everything vocation that can wield any weapon. You unlock it via the side quest "The Sotted Sage" involving Lamond (around the Volcanic Island / Checkpoint area), then equip it. Well worth grabbing before you hunt the maister teachings (203958047), since being able to use every weapon type makes several of them far less faff.