Mine had PVA glue in.
I cut a larger hole to fit a transfer pump into it. I used a short hacksaw type blade - only stronger - to do this (it's designed for cutting wood roughly and quickly), after drilling a load of holes as a guide and to make the cutting easier.
This larger hole makes it easier to jet wash the insides of the IBC. I only used a cheap jetwasher, and it was fine.
I just used a load of black-nasty (gaffer tape) to re-attach the circular piece I cut out, with holes drilled through to allow for the transfer pump hose and electrical cable.
I also spray painted my IBC a dark green, because the light encourages algae growth in your tank; but prior to spraying, I put a line of masking tape up the side of the IBC, so when the thing is spray painted, I pull off the masking tape, and I can see how full of pure water the IBC is.