In article ,
"Anode" writes:
Thistle undercoat plaster; manufacturer says if necessary to achieve the
required thickness, build up basecoat in 11mm stages.

If applying the base coat in two layers, at what stage should the second
layer be applied? Is it when the first layer has just become firm but not
yet gone hard, i.e. when the first layer is at the same stage you would let
a base coat get to if you were then going to apply a top/skim coat?

That depends what stage you personally would do that!

With bonding coat, I would suggest anytime between when
it's set and when it starts drying. You don't want any
chance of pulling it off or having the coats slump, and
you don't want the first coat sucking moisture out of the
second coat. Make sure the surface of the first coat is
roughed up to provide a key, although bonding coat would
probably stick well even without. If you do end up leaving
it to dry, then you will need to PVA before doing the
second coat.

Can't comment in the case of browning coat, as i haven't
ever used it.

--
Andrew Gabriel