May I suggest you buy the Andrea Black paint set- they're usually available through Amazon or can sometimes be found on Evilbay.
It's a great way of getting used to applying three layers- For 28mm I would start with the darkest tone, then skip one then the next lightest etc. That way you will get used to the sorts of tonal quality of your highlights and will be mixing with confidence in no time.
I'm with Plynkes with regard to dry brushing. Though it is possible to get a decent black that way. The pic below shows a Hospitaller base where the horses, mail and the 'robe' were dry brushed and then heavily washes a few times in Badab Black Citadel Wash:
Close up:
Hope that helps a little?