Skimming Video. A quick demonstration showing how firm pressure can help. Don't worry about trowel marks or the finish - just concentrate on obtaining a flat even coat. The rest will become possible as the plaster firms up.
Skimming is definitely not a case of applying the plaster and smoothing out immediately – there are many situations that can only be resolved in the later stages.
It is also not a case of just moving from one stage to the next. Progression through the stages is determined by how quickly the plaster starts to firm up. You move from one stage to the next once the plaster has firmed up and gone tacky. Many beginners try and do too much too soon and are often surprised at just how much can be achieved when the plaster is quite firm.
If at any stage you do not see any improvement then this does not necessarily mean there is anything wrong with your technique but probably that the plaster is too wet. In the early stages the objective is flatness not smoothness. The smoothness will come later – but only if you have achieved flatness so do do always remind yourself of the objective of each stage