You do NOT need to earn 2 times the experience of the 2nd place player as told by the results screen. I got this achievement in an IS-2 with the Iron Will operation active; I only earned 300 more points than second place (1400 vs. 1100) but still earned the achievement due to the bonus XP from the operation. (Iron Will gave out 2,000 experience!). Furthermore, every day, the first battle in a given tank results in 2x EXP for the first victory, and this too can be used to attain this achievement. A possible way to exploit this would be to wait until relatively near when the daily EXP resets and go for it then, since most other players will have gotten their daily 2x by then.
Also, you do not need to win or even have the most EXP in the game. All you need is to beat the 2nd place person in your own team, enemy EXP does not matter at all.
So with this knowledge, choose an operation that give bonus EXP and play your heart out, preferably in a tank you are very familiar with.