John Rumm wrote:
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Stick a batten either side to set the depth, then all you need do is
slap the stuff up and rule it off against the battens. Once you are
happy that it is level enough (final tweaking can be done at adhesive
spreading time), let it go off a bit and pop the battens out, and fill
in the gaps.

You can also just fill alternate bays, let it go off,
remove battens, and fill in in between. As you say,
it's a good cheat.