I first primed the Space Marines with The Army Painter's Ultramarine Blue. I then proceeded to "paint" the miniatures via Sharpie pens, afterwards dipping the models. Unfortunately, the dipping media did dissolve some of the pen marks, so I had to reapply after dipping. The colors white and red were a pain. For red, I first had to color the spot white, then add the red afterwards. I also had to use flesh paint for the faces (Sharpie doesn't make a flesh-color pen).
To see how cheap I could paint them, I decided to try out a cheap acrylic paint for the base. I now know why good acrylic paints are so important. Even after more than five coats I could still see some of the original color underneath.
The crackle paint I used did not work very well for the bases, and the only noticeable crackle effect was on the Dreadnought's wide base.
I have never been good with decals, and the Ultramarine ones were the worst. The bunched up and generally look poor, especially with the frost effect that decals can sometimes get.
Ultramarines were a good candidate for this method due to their blue color scheme and gold trim. I found coloring the cape white, then coloring it red was a waste of 25 minutes. I think the Dreadnought turned out the best of all the models.
I just purchased a Build+Paint Landspeeder that I will quickly paint using the same method. I'm curious to see how quickly I can complete it using the lessons learned from these models.