I have found this to be true with just about every guy I have ever encountered with a large dick. It's like they've been told that large dicks are so important and special that they've never felt the need to actually develope skills in bed... in their mind they've got all the skillz they need.
I wish I had the answer for you, but it's the same old how do you teach an old dog new tricks... then again maybe you do it like
this - I love this story.