Never tried blacklining in conjunction with dipping.
As for Strong vs. Dark (I use Minwax Polyshades Antique Walnut and Tudor instead) It's simply a matter of the colors involved. I use Strong/Walnut for things that I want to have a brownish hue. generally this is natural colors, yellows, browns, tans, etc. Tudor/Dark I use on things where a brownish tint would look wrong. This often is things like greys, armor, reds, some greens, etc.
These are by no means hard and fast rules. I've done some greys with Strong/Walnut and when you have dark brown fur and want to add a strong contrast Dark/Tudor is the right tool
If you'd like to see my take on the brush-dip method I've made a tutorial here...
http://chicagoskirmish.blogspot.com/2012/01/with-liberty-and-brush-dipping-for-all.html...with lots of pictures of strong vs dark near the bottom.
One thing I will say is that I started off using Walnut for most things but now I tend to reach for Tudor first. My recent Necromunda Van Saar and Sedition Wars Vanguard (on the blog as well) were all done with Tudor.