Promoting your business on SFN is fine - you got it absolutely right in the other thread by mentioning what you do without posting a link. You can put a link on your home page with any other information about yourself or your business. In your case you could add testimonials, pics of products, vidoes of installation, working models etc - the list is endless. Then all you need to do is pop into a relevant discussion and mention what you do in the course of the conversation and ask people to look at your page. We just don't do links all over the place as otherwise it can get 'spammy'.
The business owners section works as long as you are active on the site and keep reminding people you are there! Basically the more active you are on SFN, the more people will think of you when they need your services. I'd also suggest a box ad like the ones on the right. If you're interested please contact James to discuss as he deals with the advertising and he can tell you about the various other options too.