Hi Tammi, this is how I do it. If the cats go into bedrooms I'd pick one of those to start on, I do one room at a time over a few days as I find it a big job. You shouldn't have to move furniture, I sometimes do but if there is enough of a gap to spray underneath it then leave it in place. If its a big object and next to the wall you may have to pull it forward a bit so that you can spray behind it. If the bed is along a wall I would pull it away enough so that you can get to the wall edge. Make sure, cats, children any other pets are shut out of the room. If there are high shelves or tables the cats might go on I spray those as well.
Strip all bedding and gather any loose clothes or fabric type things the cats may have slept on, get these in the wash on a hot wash. Check inside drawers and wardrobes, if there is signs of cats having slept in those then I'd wash anything they may have slept on, if need be empty out drawers and wardrobe so that you can spray inside them, put ok clothes into a sack and any others into a sack ready for hot wash. If you have woollens you can put them in a freezer for a few days and that will kill fleas.
Clear as many loose items from the floor as you can. Hard objects can be dusted off or hoovered if its electronic equipment.
Some of the insecticides are usable on matresses but some say not to, it will say on the can if you can do this. If you can't use it, you can get a small hand held steamer and steam the mattress or there are silicone based flea sprays, Wipeout and another called Flee, these are ok to use on a mattress.
Start in a corner, half bend over so the can is about 25-30cm from the surface, check on the tin it will say the best distance. I start with the join between the floor and the skirting board, go in a bit closer so you get it well into any cracks. Once you start spraying adjust the angle of spray so that its hitting the join.
Walk slowly along the line of the wall (forwards or backwards whatever suits) keep the spray continual if you can, spray around, behind and under furniture on this wall, when you reach the corner, have a rest or turn and continue along the next wall, keep going until you are back where you started.
Once the edge is done, do the floor, start in a corner opposite the door, come along the wall line again about a foot in front of it, when you reach the far wall take a step backwards and keep going back to the first wall, step back and continue until you reach the door, exit without letting the cats in, close the door and check the washing, have a nice cup of tea, get a bit of fresh air, wash your hands.
Take a deep breath and start on the next room!
It will say on the can the length of time before you can go back in. I'd still keep the cats out for as long as possible, even to the next day if you can, once the allocated time is reach go in and open the windows wide to let fully air the room.