For the airbrush, if you're using acrylics, just flush & shoot some water. Follow up with some 91% isopropyl alcohol to dry out the water.
Water and laquer thinner do not work well when mixed. The alcohol will evaporate the leftover water and enable you to use the laquer thinner so you can really shine it up.
If using oil based paint...... laquer thinner, mineral spirits. I most always finish clean up with laquer thinner.
P.S.
When finished cleaning my airbrush I always put some Break Free cleaner*lubricant *preservative on the needle before putting it back in the brush.
With a model.......
Well, hairspray is hairspray. Spray some on your hair. You wash your hair to get it out and you don't actually need any shampoo. Looks like water is the key.
If you want to remove it from a model, use a couple drops of dish washing detergent to some water (I use distilled water) to let it flow better and give it a good brushing.
Using alcohol may or may not cause the paint to peel or fade, but it won't hurt the plastic. Without a doubt, laquer thinner will remove the paint and destroy the plastic too.