A different ironing method is to put the just-glued blank into your planing form and iron it straight.
I've tried that as well as the heat gun.
What finally helped me get a really straight blank was a device called the tensioner, described in Ray Gould's recently published "Tips and Tapers". Essentially two opposing drill chucks on threaded rods which clamp either end of the blank , which is then straightened, in part by cranking the chucks apart and then keeping it there until the glue sets.

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LIVE TO FISH, FISH TO BE ALIVE.