It sounds like you know the anatomy, you just want to know what to do with it!
You definitely want those stabilisers to be strong. They affect hip stability, but if you are reasonably active (walking, running, etc.), they will probably stay strong enough to do their jobs without any special targeting. (These muscles allow you to balance on one leg without falling to either side, and pull the leg in and out ever so slightly for stability in walking/running). Your hamstrings have more to do with knee stability, but the more stable the whole package is, the less direct stress you put on joints. So, stability is good!
Beyond strength, bodybuilders do try to define those muscles. But, I don't think figure competitors try to draw attention to it much-- their goal is to enhance the shape of the whole leg. The goal now is to have a smooth, tapered look without too much muscle separation. I am not sure what kind of look you want. I would be interested to read what 6-pack Girl and ItalianAngel have to say about it, since they know much more than I do.
This is Valerie Waugaman.

She clearly has trained her adductors. You can see she has an "S" shape to the inside of her thigh.
And this is Juliana Malacarne.
You can really see the definition in her abductors, and in her older pictures her adductors are really trained to give the "S' shape to the inner thigh.
As far as using machines targeting those muscles, it depends on how those muscles respond for you. I am sure some people get good growth just by doing movements that force those muscles to stabilise. Others may have to really hammer them.