Walls and Ceilings - Knockdown texture for ceiling

What is the best way to do this ... I have a texture spray gun and compressor

thanks

Thin the joint compound down to the consistency you need and spray it on [a slatter coat], let it set a little bit and then take a wide drywall knife and run it across the texture " knocking it down"

How much air pressure is commonly used?

I don't remember off hand :o 35-40 psi should be a good starting point.

I typically thin my joint compound to a consistency that: when I drag the tip of my finger through it, the sides cave back in quickly, but I can still see where my finger went through the mud. I run my compressor around 40ish psi, depending on the consistency I'm looking for. Shoot the splatter coat, then wait until it starts to dry before pulling your knife over the tips (very lightly). It's a fine line between too wet (smears all over) and too dry (won't knockdown without crumbling). Depending on your substrate, different sections will dry at different rates (over raw drywall dries faster, over paint dries slower).

Once finished and dried completely, I sand lightly to eliminate the roughness - then prime/paint.

Nice thing about texturing is, if you mess up, you can always scrape the compound off the surface, and start over. It's a messy, messy job - lay down tarps/plastic/whatever on the floor, tape off your windows and anything else you don't want to clean up later. When you're sanding, turn off your A/C unit to avoid the dust clogging up the system.

Thanks for the PSI info and the tips ... I am assuming that that on the texture gun you turn to the largest hole for this ... is that correct?
Thanks again!

Ya, you want to use one of the larger holes but it's somewhat dependent on how heavy/fine you want the texture.