Shannon Xerri
It's all about targeting motivated sellers, people that want to deal with you.
There are many different sources such as:
Probate
Absentee-Owner
High Equity, Deed Date 15+ years, Over 65 Homestead Exemption
Pre-Foreclosure
Code Violations (If your state is open records, request under the open records act)
& more
You can purchase the aforementioned information from various list providers. Alternatively, you can query it yourself from your Central Appraisal District or through MLS.
As you stated in your original message, driving the subdivisions yourself, is a great way to produce leads. Often times referred to as "driving for dollars" or "dig leads".
Once you have chosen the type(s) of motivated sellers you would like to target, you need to determine your criteria to further filter through your leads.
For example I wholesale here in Texas. Begin to break it down further. What cities would you like to target? In my case Arlington, Mansfield & Fort Worth. Within those cities, which zip codes, what sort of houses, bed/bath/garage, sq footage range, tax assessed value, year built, rent rates, exterior type, school districts etc. This process enables you to break down raw data into something very targeted. Once your data is properly filtered its all about putting yourself in front of these people.
You can do this by taking your lead data and building a simple database in excel. This database can be uploaded onto various mail fulfillment centers, such as click to mail, where one can upload an excel database, and the website will automatically send out the letters for you by "mail merging" your database. No licking envelopes, writing addresses or going to the post office for stamps.
I hope that has helped provide some additional insight, best of luck and please don't hesitate to ask if you have any additional questions.