My trowel keeps sticking to the cieling.. Why
Answer
Well that's a different problem!
I guess it is due to the suction - the front, leading edge of your trowel should be 10 -15mm away from the surface, or even more if you're using a stainless steel trowel (as they're liable to bend and curve more).
Then you will be using the trailing edge of your trowel - rather than the whole area.
Get the angle correct and you should feel you're trowel glide across the surface.
A too severe angle (front leading edge too far away from surface) and you'll feel it scrapes - if the trowel is too flat it will drag.
Take your time to find the differences the angle of your trowel gives, whilst keeping firm even pressure. Then your speed will soon increase.
Paul