VW Special Tool #3424 a.k.a. The Spreader Tool (required) - available for $10 from Autotech or $20 from Zelenda. Or, if that's not available, a 1/4-inch slotted screwdriver bit in a 1/4 ratchet drive can work too.
flat headed screw driver and a hammer
You'll need a f@@king strong screwdriver. Mine would'nt budge.