Under the tankers fuselage, between the wings and the boom, there are some black marks. No idea what that is. But when i place them in the center and about two thirds up in the window above the hud, i find myself in a very good position for tanking. From there it's just regular formation flying, keep your eyes on the marks and the boom will take care of itself.
The key is to keep that formation with as little control inputs as humanly possible. Practice formation flying, not just in the tanker formation (behind and below), but all kinds. Fly side by side, echelon, left and right. Try to change formation controllably. For example, fly echelon right formation and slowly slide over to the left side. Don't just break the formation and then return to a new one, but keep control of your position even while moving, if that makes sense.
The first few hours i tried, i totally sucked before i got the point: Fix the other plane with reference to your cockpit. Make it look like it's painted on your canopy. Mess around a little (gently) with your flight controls to learn which input is required to move this 'canopy painting' in what direction (this depends on what formation you fly of course). When my muscle memory slowly started to learn this skill, I realized that the throttle simply controls my distance to the plane, NOT direction, as that is done by my steering hand subconsciously.
Practice flying 60 degrees to the other plane, that is 10 o'clock or 2 o'clock from you, and keep constant distance. Then you will find that flying in the refueling formation is actually quite easy in comparison.
The more you try, the smaller amount of control inputs you will need. After a while it seems you don't need to move your hand att all, all you need to do is 'think' where to go. And suddenly you can fill up tank after tank without a single disconnect.
My method for tanking now looks something like this:
1. Join formation with the tanker (black marks between wings and boom fixed two thirds up in my 'above-hud-window' or whatever it's called). Distance does not matter here, but you should be able to see your reference point of course.
2. Trim out! This is important because if you don't you won't be able to relax as much in your hand and your moves will become jerky.
3. Keep the marks fixed and control your distance using only the throttle. Close in on the tanker gently.
4. When the boom gets in the way, ignore it completely, keep looking at the marks to keep them fixed at the exact same position at all times.
5. Keep controlling my distance using ONLY the throttle as input, and the color gradient on the boom as visual feedback. My eyes are fixed to the marks on the tanker, while observing the boom color in my periferal vision.
6. Tank is full.
If my "black mark position reference" does not work for you, try another one. It might be my TrackIR settings that's distorting my viewpoint.
Perhaps this is useful tips? Perhaps not.
Anyway this is how I learned it and it actually works consistently.
