Not trying to be negative, but the majority of contractors are not even incorporated so trying to convince them they need a facebook page or even a website may be a hard sell unless they are very established and use other services like attornies or accounting firms. Contractors in general, are usually have less than five employees or less. The larger the company the better the chance for success in what you are trying to accomplish. If the contractor doesn't just run the business and actually does the jobs himself I think you are going to be surprised that you will get turned down probably 90% of the time.

Many contractors live paycheck to paycheck and don't have additional funds to try another platform.

Many contractors do not know how to automate their business in general by using services like paypal or a credit card company.

Many don't even have a facebook account and find it daunting to even get on the computer.

All hope is not gone though. Here is a list of things to consider when pursuing contractors.

1) Find trade shows where they advertise. If they advertise in any way and it's consistent that's someone that understands the value of additional services. For instance, in my industry we have the Apartment Association i.e. Texas Apartment Association with branches throughout the state. Become a member and you will have a list of all the contractors in that industry.
2) Angie's List has contractors with ratings. It will show the volume of their reviews which could help you determine how well they do financially.
3) Buy contractors list
4) Start a business network on LinkedIn. I started a property management group a couple years back and now it has over 4200 people with very little effort.
4) Have a landing page targeted to contractors where they can get information by providing an online submit form. Show them benefits of why your service is good or great and then ask them specific questions to see if they are good candidates for your service.
5) Provide a free service or free consultation to get your foot in the door.

At the end of the day you have to be creative in your approach. As far as results that will depend on your approach, the market you work and what services you provide.

There is no easy way to run a business or to attract business. Once you find your niche stick with it and tweak it from time to time to get the best results.

I've learned that if I get one customer the best way to get more is to provide that paying customer with the best experience possible and then ask for a referral. Don't you think other contractors know other contractors? That's your secret to your success right there. Provide outstanding service at a reasonable price and then ask for the referrals. It works so well for me I don't do advertising.

Be extremely careful in making claims for SEO that you can get them at the top of the search and you own website(s) don't show up at all.

SEO will mean nothing to most contractors and if they do trust you to get better results you had better deliver or your reputation will be ruined very fast. Especially true if you are working a primary city and not nationwide.

Last and final thing to look at is to see what your competition is doing to get business. Find a way to better your service and outshine them in the area for amazing results.