Just an addition to what BK said about the toothpick. If you dampen the tip of the toothpick with a little isopropyl alcohol it helps dissolve the paint it touches so the paint won't chip as its being chiseled away.
You can also avoid the paint creep under the masking by putting thinner, lighter layers of paint on the canopy so the paint dries almost immediately after it lands. That way it won't keep flowing out from where it sits.