Hi, Raoul!

Personally, I have found that, to teach the children, one must say "e" and pay close attention to where one's tongue is, that is, the tip slightly curled down and pressed against the bottom teeth. Then one says "oo" with the lips, putting the tongue in the "e" position.

I found the "r" much more difficult. In the US, where there are so many Spanish-speakers, it's often trilled instead of gargled. My girls have already noticed the Canadian hockey player who they thought was ethnically Chinese because the sports commentators kept talking about Patrick Wa. Then they saw the spelling of his last name: Roy. Aha! French Canadian!

The word "rue" is the acid test. Lots of English-speakers pronounce it like Kanga's baby in Winnie-the-Pooh...

Regards--
Mary Anne