It's not so much "difficult", process wise, as sometimes they just refuse to breed and raising the fry takes a lot of work with the water changes and frequent feedings and what not.
Genetics wise, there is LOT of free information out there and people are always happy to answer questions.
The only dragon vailtail I know of for sale is in Australia and they won'r ship out side Australia.
That could be something for you to work on, youself, though. You can buy a black dragon HMPK like this:
and, say, a blue female(most 'female betta' you find at petstores are vailtails unless stated otherwise).
you should get some partial dragons(you may get lucky and some may have full coverage) and then breed the best two fry together.