It you're like me, you take pains to mask of a canopy. Fit in there nicely. Then, run the extra thin tamiya along the seam to lock it in place. As a last step, you peel the tape away and..arggh. Dust on the inside!
I found blasting out the cockpit as well as the inside of the canopy, before attaching it, with compressor air makes a difference. Something I never really thought of before, as dust does build up a lot inside the cockpit along the way.