Why not use the Mr. Surfacer 1000 for primer?  It is a personal taste for me but I find that Enamel and laquer based primers have some bite into the plastic and metal and are much more durable.  I am very abusive to my kits during the weathering process and have been known to rub right through to the plastic.  I use Floquil railroad enamel primer through an airbrush and it has the smoothest, toughest finish I have ever seen.  Stinks to high heaven though and it is a pain to clean up.  The Mr. Surfacer spray can should give similar results and have less cleanup.  If you spray it now it should be cured by the time your airbrush arrives for the rest of the paint.  I usually wait a week while the primer cures.  Just a thought as you have it sitting there.

Looking good.

Dennis