im not great with a double hander myself ( as i only break it out once or twice a year - which is not enough....)
A few things that work for me.
Single spey i was useless at ( as i kept 'breaking anchor' ) so i was shown the circle c ( systained anchor) - makes life MUCH easier.
I have tried all sorts of lines and a few rods.....
the easiest setup is the one i have now, that even a numpty like me can whizz a cast out.
what is it i hear you cry ?
A Shakey oracle scandi 13ft 9 with an airflo rage compact ( 600 grain)
the line is one weight heavier than 'reccomended' but it loads the rod really nicely and if you do a nice slow controlled cast it flies out !
ive had way more expensive rods, and way more expensive lines but this setup is 'the dogs'
when i was invited to go to the spey etc i would feel really nervous as i was a 'beginner' - no longer ! First trip with this setup and even the gillie seemed impressed