I want to know how to apply thermal paste to i7 3770k without having air bubbles.
Try This Way, Try That Way, Blah, Blah, Blah!
The best thing to do is try whatever application method you desire to use, clamp down the heat sink, then pull it, and inspect the thermal footprint, that's the only way to be sure of exactly whats going on under that heat sink.
That will also reveal the surface contact between the heat sink base and the CPUs heat spreader, is it cupped or bowed, irregular, etc., indicating uneven clamping pressure, or where you may need more or less thermal compound.
Everyone seems to assume those contacting surfaces are perfectly flat, but they are not!
The closer they are to being flat the less thermal compound you'll need!
You want to use as little of thermal compound as possible, thinnest layer possible to attain full coverage, and you'll only know for sure by pulling it and inspecting the thermal footprint.
Too much thermal compound is bad, is can insulate instead of conducting the heat, you are only using the thermal compound to fill the microscopic imperfections that leave air gaps (Bad because air is an insulator), between the two surfaces, the heat sink does the cooling not the thermal compound it is only a conductor.
It's always best to know what's going on under that heat sink, than to wonder, knowing is better!
Different thermal compound consistencies act different when clamped under pressure, so not every thermal compound can be treated the same in application methods.