Primer choice

To find surface defects: Tamiya sky gray XF-19 (acrylic).

Under white: any metallic silver.

Under yellow: white, or silver then white.

Under orange: same as yellow unless you want a slightly darker shade, in which case use a brown.

Under red: same as yellow unless you want a slightly darker shade, in which case use a brown.

The key to using acrylics successfully is to have a CLEAN plastic surface. I suggest washing using Simple Green or Windex, rinsing thoroughly with distilled or deionized water, then wiping down with ethyl, denatured, or 90% isopropyl alcohol just before painting. Once you start painting, don't touch the model with your bare hands. 

I use Model Master flat white enamel to prime most of the time.  As long as the primer coat is cured, you shouldn't have any trouble using aryclics, lacquers or enamels as the top coat.

Sometimes you might want to prime with something other than white.  Using a darker color, or a complementary color to the top coat, can produce interesting effects.

The Tamiya "fine" white that comes in a rattle can works great, drys fast.  While I have not used it, I was under the impression that the liquid primer that you refer to was for fixing scratches and seam repair as opposed to priming an entire model prior to painting.  Other people love Mr. Surfacer thined with laquer thiner and then sprayed.