I too want to work with a marketer for my web design business, but I've found that many simply want to do early stage lead generation and then "drop" the clients over to me as a client manager, which doesn't reassure clients that marketing promises will be upheld... I think the best (development) marketers are people who invest in learning the nuances of the business (e.g. knowing there are quite distinct differences between coding in ASP.Net and PHP). The same can be said for tech recruiters... aY yAY yAy... lol.
As a dev I had to learn marketing inversely, to allow me to better understand the process of ensuring clients a smooth and trust-worthy process... In running my business I have to daily be involved in absolutely every aspect of it (without being too controlling of course) because managing delivery and client experience is a key to gaining and retaining new and follow-up work.
The best method of self-marketing/promoting I've found is to build my own products/portfolios that represent what would be useful and engaging to new potential clients. Working product demos also help marketers to better be acquainted with what they are ultimately selling, and make intuitive screen shots and presentations of the products in support of their efforts. That way I also have a template I can build quicker from, but I also demonstrate to clients that I can actually do the work.
IT is far too complex in presentation these days; many clients are not focused on tech stacks, methods, tools, services, or things developers are usually focused on. Modern clients are usually most concerned about their requirements and business needs, a marketer should focus on being a translator in a way when it comes to marketing development work, linking that work to productivity, progress, and things that satisfy requirements and provide benefits in a clear and usually less-technically inclined manner than a developer would detail a solution...
E.G.... We keep selling "the cloud" to everyone, but if you ask a client what "cloud" is they simply don't know/don't really care what it really is, as long as it fulfills their business goals.
In a world where people are using imagery alone to market their capability, the real working examples of what we do as a company are often what wins us new work.... Even if we don't win new work, the products we build usually end up being valuable and highly useful to us ultimately in real life.