As a bit of background to my post, I started playing poker in small stakes cash games, and more recently in live cash games too, however MTTs have been my primary online game for the last 18 months or more. I've dabbled in PLO, HUNL and a few other formats with limited success. I have about $7,000 in online winnings over around 1300 MTTs at ABI $10, a sample size which may or may not be relevant to this post or in general. 

Coming from a cash background, I'm pretty comfortable hand reading and playing postflop in the deep stacked early portion of the tournament, however I feel that I have big leaks when it comes to the <40bbb stage, specifically in deciding whether to fold/call/3bet/4bet facing a raise or 3bet, and picking spots to 3bet bluff. In a full ring tournament I typically find myself putting raisers on strong ranges at all times and thus folding some pretty strong hands myself in LP, when I get lost and feel my hand is too weak to 3bet but that it's also incorrect to flat call with shortening stacks/OOP. Conversely, when I do attempt to open up my 3betting range, I often find myself getting played back at or running in to hands, wasting some sizeable stacks in the process. My spot-picking is obviously off here, so I revert to a nitty cards-oriented late game, which has served me okay in part but is certainly not optimal even at low stakes. Since this part of a MTT is where the money is made, it's kind of a big fundamental part of my game that I need to improve on. 

So what I'm asking for is suggestions on how to work at this. I've tried reviewing my HHs for spots where I could have made a light 3bet, or ones where I've tried getting out of line and failed, but these hands are usually as difficult on review as in game. Training videos are helpful and the explanations make sense at the time but ultimately I can't seem to translate what I see in them into an overall preflop strategy. The same goes for discussing hands on Skype etc. 

I realise this is a pretty vague/broad post, I guess what I'm trying to achieve is to break out of the solid, ABC style and start finding spots where I can pick up chips without always having the goods. Which is what seems to separate the really good players in any tournament. Preflop raising wars feel like a bit of a guessing game to me, and usually I tend to end up getting myself on the wrong end of them!

Cheers.