M.C.
My DD wasnt a big prune fan either... pear or apple juice went down MUcH easier for her. She preferred plums too. Apricots, peas, and spinach are also good anti-constipation foods. Also, if you are giving her cereal that can be a culprit... Especially if it's rice. (Although, any cereal with iron in it won't help her constipation any...)
When my DD got really bad, I would give her a tummy massage. After a nice warm bath, I would use the heel of my hand to rub small clockwise circles on her tummy. (Concentrating on the area between her belly button and pelvis, and only using as much pressure as you can comfortably put on your eyelid.) I usually worked from left to right, then some longer strokes. Then I bicycled her legs for a little while, before repeating the massage. I almost always got a big, nasty blowout within an hour or two of doing this. (Just a warning... Use one size up in diapers, because when that blows it will be NASTY! Lol.)
Good luck!