>>6731620Silly putty, make sure you wash it off with warm soapy water first though as it has these oils on it from how its processed.
Also, you can use something like this curved masking tape as well for hard edge camouflage, it's made by Tamiya.
Another way is to cut out the camouflage patterns with some standard printer paper. After you do this, roll up some small pieces of tape into circles, and place them on the bottom of the paper, and then place it on the model. It will leave a clearance of about 1mm which you can use to achieve a nice soft edge camouflage scheme, good for luftwaffe aircraft.