Renovating our house, need some plastering advice please

Hi, I am new here and hubby and I are in the process of renovating our home. We bought a 3 bed, double brick/tile house and we are in the process of adding double brick, concrete slab, games room on, connected to the house but at the back of the house, then on the top of that we have another story about to go up, with a suspended concrete slab. This will be a 4th bed, ensuite, retreat, and that is also double brick/tile. So basically we have a big 7.5mtrs x 8mtrs 2 story box with 28 (I think 2.4mtrs) bricks internal floor to ceiling height. Down stairs has 4 walls, 3 brick piers and that is really it, upstairs obviously has walls seperating the bathroom from the bedroom, bedroom from the retreat. SO they are the stats.

So here is my ??

How hard would it be for us to plaster the walls?? Is it a 2 part process?? DO you need to use some kind of sealant on/in/before the 1st coat? What tools can you buy to make an owner builders life easier to plaster without having to call one in?? Can you buy a product that you only have to use once and get the same effect?? Can you buy a paint on thing that will give a simular effect?? How much do you think this kind of an area would cost to hire someone to do it for us?? I live in Perth West Australia..How long is it inbetween coats or painting??

The reason I asked this was because we were going to leave this for a later job, we just wanted to get the roof on sealed up so we could get the electricity connected and aircon in, and plod away at the rest, but we were informed we have to plaster before we have the electrical work done. So we are trying to find another way if we can..

Any advice you can offer is much appreciated, we are very new to this renovating game but learning alot

Also do we need to do anything to the suspended slab, as it is on 1 side our ceiling, so it obviously needs painting or something but do we need to plaster that too?? I wouldn't think so

Thanks again