Knock on the Door of a Pre-Foreclosure?

Has anyone found success in buying pre-foreclosures this way? That is, to knock on the door of a home in pre-foreclosure and seeing if the owners are in a position to sell. Also to knock on doors that are behind in their property taxes. I see in Bill O'Rafferty's blog that he recommends it, to take a female with him to make things less threatening, and to expect a wide range of responses. His greeting statement is: "Hi, we are looking to buy some houses in this area and are wondering if you know of anybody in your neighborhood that was looking to sell their house"

In Montana, the culture is rather low on hospitality and people with rough edges abound. Likely 80% of homes have a loaded gun and 30% of vehicles. That's just how we roll up here.

Also, I am really tall and big -- former offensive lineman -- although my face isn't scary. My wife is not willing to go with me since this is my business/dream and she is working hers. And Winter is coming -- in Montana.

I tend to think that letters sent to these properties are likely not very effective. I have sent about 40 and gotten no responses.

I intend to have a business card and info about:
short sales, loan reductions, the foreclosure process, lawyer referrals, RE agent referrals, and my desire to make an offer. I want to either wholesale the deal or do a sandwich-lease option ala Greg Murphy.

Any tips will be appreciated. Especially from experience.