I have just finished putting the topcote on the walls in the bathroom.
I have found it to be fairly easy.
I used Basecote 45 for the joins with paper tape, and Basecote 45 again on top of that.
Hard stuff to rub, then a thin film of Topcote over that.
As it is the bathroom, a lot of it will be covered with tiles, so it has been a good place to learn.
Next I will be doing the waterproofing.