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Just did my first ET pour, based on the helpful advice here its gone well!QAfter say 24 hours, could I clean out the pot holes with a sharp blade instead of waiting for full cure and drilling?
As @Adam_MD says. 24 hours is not enough. I've made small impressions in the ET as it is still malleable at this stage. A bare minimum is 48 hours, but preferably 4 days. Personally, I would drill the holes with a stepper drill (however, I do the 3mm LED hole manually with increasing sized drill bits - 2mm, 2.5mm then 3mm swizzling the drill bit in my fingers).