canopy dust

If you want to paint with the canopy in place, might try tacking it in place with elmers white glue and clean and glue it tight after.

If solid one color paint, mask both sides so you can paint off the model and install after.  Dry fit to suit before masking and painting.  Mask the pit on canopy rails with soft foam, tape or combination.

If you need (or wish) to attach your canopy before finishing, you essentially need to carefully 'seal off' the cockpit enclosure to create a barrier. Further construction and painting (and handling) will almost always generate those particles...which will then almost always be drawn by static to the canopy area.

White glue is probably the easiest sealant to use. Be sure to fill any gaps around landing gear bays (especially tailwheels, where applicable), engine intakes and so on. It usually only takes a minute or two, but can save a lot of grief later on.

I certainly have had the problem.  While I have used my airbrush to clean completed models, especially sailing ships, I had not thought about it for cleaning out cockpits!

In the case of this Eduard P-38, the canopy consisted of a complicated set of pieces that precluded attaching them after paint. As it was, I did a lousy job of putting iot all together and thus needed to paint in place but I will take the idea of painting off the model to heart. Thanks.