Mixing custard up is hard work

Saturday I had some WAM fun in a hotel room and a paddling pool full of custard.
Well that was the plan but mixing all the custard up was a nighmare and most of it didn't mix properly either and I ended up with a yellow puddle in the pool.
The only way I could get it to mix was a packet at a time in a jug! As soon as I tried to mix loads at once it wouldn't mix for some reason!
Oh and 120 packet of 7p custard do not even cover the bottom of a paddling pool btw.
Anyone else found mixing loads of custard hard work?
Well that was the plan but mixing all the custard up was a nighmare and most of it didn't mix properly either and I ended up with a yellow puddle in the pool.
The only way I could get it to mix was a packet at a time in a jug! As soon as I tried to mix loads at once it wouldn't mix for some reason!
Oh and 120 packet of 7p custard do not even cover the bottom of a paddling pool btw.
Anyone else found mixing loads of custard hard work?