K wrote a tutorial detailing his "Multiple Annas" effect!
Step 2 -insert kid
Step 3 -keep shooting in the same direction (it will make later steps easier and the lighting will be the same too)
Step 4 -open up pics and pick the best one for background and composition. do all of your image adjustments here before pasting in other images
Step 5 -on the reject pics make a selection around your subject and hit copy
Step 6 -paste onto good pic
Step 7 -adjust levels and color to match background (usually doesn't take much)
Step 8 -depending on your background, use the lasso and delete all of the extra stuff from the pasted image.
with an autumn background you can be very sloppy and no one will be able to tell. you can be a perfectionist if you like, but who's got the time.
Step 9 -for that extra dash of realism, use the airbrush on a separate layer to blow in a bit of shadow.
I usually use straight black and turn down the opacity on the layer to soften and blend it.