Intuition let me down

I played this game a few days ago.

http://www.chess.com/blog/iwijetunge/reedsburg-open-2013

I was so sure that Black could not prevent me from infiltrating the queenside, I thought I was winning.

But black managed to plug the queenside, and the game was a draw.

Given a pawn structure, how does one go about answering the question.

Can I infiltrate?

Looks like b3 and bxc4 will work. If the b-pawn recaptures, enter on the a-file, if the d-pawn captures, the temporary sac of d5 allows the king to enter on d4. If black captures on b3 and plays a5, then an eventual sac at c4 should work, though you’ll have to be careful because of the passed a-pawn.