B.P.
My son was also a big fan of the soft spout sippy cups. Refused a hard spout. He went straight to no lid cups. This may work for you.
We also struggled with teaching him to use a straw, but it became necessary because it was the only way to drink on the go since we no longer had the soft spout cups (he kept ruining the tops from chewing on them). My sister just got him to drink from a straw a couple of weeks ago. She just told him to put the straw in his mouth and "give it a big kiss." It clicked with him and he's been happily drinking from a straw ever since. Hope it helps you too!
B.