I had a hole in some drywall that I repaired with spackle paste. I sanded it down so it is level with the existing drywall. The problem now is that the spackle is smoother than the surrounding drywall. How can I create the same texture in the spackle so that it looks seamless when I paint over it?
If the drywall has a substantial amount of texture, you'll find 'texture in a spray can' at your favorite big box store. Probably get the one that says, "orange peel" on the label. Like this: spray texture
If it's just a tiny bit of texture, use a thick nap paint roller and start putting coats on. You'll have some texture in no time.
I found the canned texture stuff to be gimmicky. What I typically do when finishing walls after spackling is mix a bit of joint compound with a bit of water. Take a brush with bristles, dip it in the mixture, hold brush with bristles facing upwards towards the wall, and run your finger through the bristles essentially flicking the mixture onto the wall. You can experiment a bit with the pressure and distance. If you don't like it, you can wipe it up and try again. Once you get it textured to your liking, you can knock it down with a putty knife. Once you repaint, you won't be able to tell.