A couple of added points to concider...things I've learned:
1. If you plan on displaying an open canopy, you'll have to attach and blend at least the windscreen portion of the canopy to the model. Mask the remaining opening of the canopy and paint the model it's appropriate colors. Paint the remainder of the canopy parts off the model. *An exception to this would be if you have a multi-color camo scheme that follows over the canopy area. In this case you may try drawing the camo pattern on the masked canopy, then airbrush along the drawn pattern.
2. If you simply want a closed canopy, masking the canopy off the model( you'll do a better job of controlling the hobby knife while following contours) as aposed to trying to negotiate and handle the model while you trim the canopy lines. Attach the canopy, fill any seems or joints, then paint your model. Happy modelling!
Greg Williams
Owner/ Manager
Modern Hobbies LLC
Indianapolis, IN.
IPMS #44084