If you are using silicone-based airbrush makeup, NO primer is best. Absolutely spotless skin, no moisturizer, no primer, no toner. This is a must.Primers tend to interfere with silicone makeup's ability to adhere to the outer layer of the skin, and that goes for traditional makeup too, in my opinion.
I honestly believe that the whole primer "revolution" is a marketing ploy to get us to buy yet another layer of goop to put on our faces. If a client needs filling, a silicone filler can be used.You really don't need a primer except for mothers and grandmother of the bride types. The MAC line filler is great for that, or if that's too spendy, the L'Oreal pink primers in the little pot are almost just as good at smoothing out the little undereye lines before appyling foundation. If a client needs color correction, go for it. Otherwise, your foundation of choice should be able to do its job on its own, If it cannot, you need to choose another foundation.
The key to long-lasting bridal makeup is not to add more layers, but to add as few as possible: the less makeup there is, the less there is to slide off in a greasy sheet as the bride dances, etc.
That being said, if you feel you absolutely MUST have a primer, I would suggest trying one of the more acidic primers out there for your normal skinned clients, like Dinair's one for oily skin (it does not dry out skin) or Bare Minerals Prime Time, rather than one of the silicone primers, at least for all-over use.
If you're building your kit, the key is to buy less, as you seem to be doing. Good luck to you!