what is the best way to texture the ceiling in just one room?

[keakar]

I have plans to put sheetrock up just on the ceilings in every room in the house, but its being done in small stages just one at a time since all space is being lived in, so there is no practical way to leave a room unfinished because it needs to be made fully usable before moving on to the next room.

my problem is in doing one room at a time, how to texture the ceilings? its going to be too expensive to rent a machine each time for each room (like $50-$75 per day) and I don't have any walls to spray to justify spending that money.

I wont be able to spray the whole house at one time, so how do you just do a small area like one 12x12 room?

any sheetrock or remodeling guys out there can give me the best way to approach this?