Playing chess and calculating variations

Every chess player, who at some point of his career considered himself serious and ambitious but never reached high level, probably tried to figure out what is the essential thing which divide strong GM´s ( let´s say 2600+ ELO points but I am not so sure with all that rating inflation issues ) and mortals like him. I don´t have simple answer to that question (because I am not strong GM), and probably there is no simple answer at all. It should be something like a accumulation of all small advantages like slightly better opening preparation, a bit better concentration, better knowledge about middlegames and endgames, slightly better calculation of variations e.t.c. So, if we talk a little just about calculating variations (according to many good players, the most important ability in modern chess, but I am not so convinced) we can divide this ability to some sub-abilities, like tactical vision, process of choosing candidate moves and ability to organize your calculation by famous variation-tree.
When I start to teach my students about calculation of variations I usually starts with ability to organise their calculation. That is possible to do with some of the exercises which contains not to much "hard to find" moves. Positions should be concrete, enough complicated, with wide branching lines but without hard tactical moves (that is suited for training of tactical vision). There is one beautiful example in famous book "Think like a Grandmaster" by Alexandar Kotov and I will publish it later this month. Every single move in solution is very simple to found but how to organise all the moves especially during a game (without moving a pieces) is very hard to do.
When I played a game against Engman R. (2185) in Swedish team championship this year, I got following position:

Click to enlarge

White to move. What to do against f7-f6 ?

The game was played in Stockholm in the match Eksjö-Aneby Alliansen  against Rochaden Umeå which we eventually lost with 6-2 (two draws, and only one whole point from diagram position). We had substantional advantage in rating on all boards (which didn´t helped us). It seems that all that theoretical introduction of this article can be employed in this position. I played a serial  precise moves which gave me better endgame, but no single move in whole combination was hard to find. The hardest thing was to organise variation tree in my mind. I will not give You the whole solution ( it comes in next post) just two introductory moves.
I played 11.Qc2 and then followed 11...f6!? . Exercise for ambitious players is to calculate trough all variations.  You can write your main line in comments if you like.
Have fun!