How can I increase sales in my small business marketing group?

[irishdude]

I set up a small business marketing group in a rural part of Ireland for similar sole traders that are struggling. It consists of 20 members offering a variety of trades and services to mainly domestic customers. We plan to make a joint group brochure and work for each other for free marketing each members business to our own individual customers thus supplying each other with new customers and markets. What other inexpensive technique can we employ other than social media, cold calling etc.