How Do You Get Best results using a Rattle Can??

why not just decant the paint from the spray can and then use it in your airbrush?

Ditto....
However, if you do spray it from the can, warm it up first. The paint will 'thin' and lay a little better. Spray verticle and make several quick passes to get coverage but not build-up. Let dry and make more passes until you're happy.

Be careful with the heating.  Try to stay within 10deg of the recommended temp.  Vertical is the best.  To get less paint add distance.  Don't get too or the paint will lay ruff and won't have gloss.  Make sure the subject is also over 72deg.

I've worked for years with those wonderful spray cans. 

I haven't always warmed them up, but hey call me crazy. 

Each can [nozzle] and paint sometimes sprays a bit different, so test the best "working" distance for you on a scrap, even paper or card stock.
I find it best to spray anywhere from 8" to 12" depending on a few conditions and variables, hence the pre-test.
Start off with 2 mist coats, just to get the part sticky with paint.
Before that totally dries, but is not tacky anymore, I lay down a thin wet coat. Just slightly more paint than the mist coat. Again after a few minutes (read can directions as I questimate usually) I lay down the second coat. Or you can let the first coat totally dry, sand, polish and then spray the second coat.

Orange peel is usually caused by the paint drying uneven. Some possibly before hitting the object while applying to heavy of a coat. Remember, spray cans are like garden hoses, they flood the model with paint. Move quickly, keep the layers thin, spray at the best temp range and don't try to cover in one shot. Spraying verticle or horizontal is a matter of preference and object to be painted. Large flat items such as car hoods, I like to spray laying down flat. Items laying down flat will have less runs in them and the paint tends to self level a bit better.

Oh almost forgot 

Shake can often and thoroughly!

Just my

Warming the can on cold days and making several (3-4) quick passes works for me, although I try desperately to avoid using rattle cans.