do i paint the inside or the outside of the canopy does it have to be masked

Mask the canopy, paint the framing the cockpit or canopy frame colour, let dry and then paint the external colour.

Painting the inside of the canopy is very difficult, usually.

You want to paint the outside of the canopy with the interior color first. After it dries paint the exterior color on.

You don't want to paint the inside of the canopy because you can see a clear gap between the inside paint and the outside paint, especially if it is a large scale model.

Just my 2 cents.

In most cases you paint the outside. If its a larger plane or has a peculiar, particular inside color you want to show off, paint the inside color first, then the outer color on top.

You don't have to mask. I do a lot of 1/72 planes and paint the frames by hand. Especially complicated ones like a Do. 217 or Heinkel 111. You can also use painted strips of decal, or buy pre cut masks to help mask. Tamiya tape is also good for masking.