You get a knockdown by splattering on gobs of texture material (I usually use soupy compound); let it start to set up and smooth it (knock it down) with a knife or trowel. You may have to experiment with it at first until you get the idea, and it isn't hard. To patch it, get creative with a putty knife and regular compoud and a small sponge.
I give more particulars on my website at www.bobf.info in the drywall topic.
I give more particulars on my website at www.bobf.info in the drywall topic.