David, You can hand straighten them while green without heat. Every day or so pick up the shoots and work on the worst bends first. Do a little at a time and wait a few more days and start again.By the time they dry(depending on R/H, could be as little as a few weeks)they will be pretty straight. Then you can use a candle to heat the areas that need a final straightening. I like to put cooking oil on the shoot before using a flame. I think it helps hold the heat, heats more evenly and prevents scorching while straightening.
With hardwood shoots I like to add color by scorching along the shaft. I do this after the shaft is cured and straight. After scorching let the shafts settle in and rehydrate for a few days before stressing them. Pat
