The following was taken out of an article by Toni Carroll, a fabric artist.
Always preshrink fusible interfacing by imersing in a pan of hot water from kitchen faucet. Let sit until it cools. Blot dry and lay flat or over rods, fusible side up, to air dry. This will insure a better bond and eliminate those awful bubbles.
I don't know if she does this only for her garment art, or for everything. Anyone else do this?