How to temporarily hold open canopy closed while painting rest of plane?

I also use the paper towel or tissue paper(Kleenix).  Dampen lightly and carefully fill the area you want to protect (I've found a set of curved tweezers work better than your fingers). I dampen the paper again just before I paint and again just before I remove it.  Also works great for wheel wells and openings in the cowling.

yup!  the thing is though if you are doing a camo pattern it's usually better to put the canopy on if the camo will stretch over it... otherwise the paper towel thing works...  

OOooohh...the wet paper towel idea is an interesting one.  When you do that, you leave the canopy off?

QT

I stuff the cockpit with wet paper towels (wrung out of course). Paint away, and then when the paint is dry, re-wet the towels and pull them out.

I've used Micro Kristal Kleer when I wanted to do this but the white glue will work just as well. In fact, I even use it when I want to keep the canopy permanently closed. It's surprisingly strong.