Hi Laks
Another option is to apply the plaster, let it start firming for a while but when it is stiff to the touch but not dry as too become porous you may be able to trowel on again to build it up in layers.
Or apply the first coat of plaster, let it completely dry after you have floated out the trowel marks, then seal the first coat of plaster with a watered down coat of sealer (as for porous surfaces) probably give it 2 coats of this mix, then trowel over again.
I hope some of this makes sense, all the best.
Regards
Dale