Jim,
Self etching primers actually contain a small amount of acid etch right in the primer. Thus spraying a self etching primer over an Alodined surface will degrade the quality of the Alodine process. Have you read DuPont's recommendions regarding VariPrime? If you had, you would know that VariPrime is NOT recommended as a finish surface for alumimum. DuPont recommends applying another primer or finish coat over VariPrime. VariPrime does not create a vapor barrier (it's porous and doesn't stop water from moving through it) and contains no corrosion inhibiting metals such as zinc chromate or strontium chromate.
Due to the two limitations above, why would you want to use VariPrime? I would suggest that you use a Mil-Spec epoxy primer, like Akzo, Deft or Sterling U1201/U1202. There are a number of other similar products. All Mil-Spec epoxy primers contain strontium chromate.
Since you've gone to the trouble to "do it right" by Alodining the material, why not use the best type of primer? There is no increase in work level for you.
VariPrime's only advantage is that it saves work for the lazy. When it comes to corrosion control, that old Bally Health Club TV ad comes to mind. (You know the one, with Cher) Cher states in the commercial, "If great bodies came in a pill, everyone would have one". The same applies to prep/paint work, if you want great results, you have to apply elbow grease. There are no "free lunches".
Cessna offers a 30 year warranty on their new airframes. Why? Because they apply Alodine and epoxy primer to every part of the airframe. It takes BOTH chromic acid conversion (aka Alodine 1201 or Iridite 12-4) AND a mil spec epoxy primer to prevent all 8 types of corrosion on an aluminum surface.
To learn more, go check out the Technical Article section of EAA Chapter 1000's web site. See
http://www.eaa1000.av.org/technicl/corrosion/corridx.htm
As for the previous lister who recommends using a "system" from one manufacturer, while good advice, it's not the "only way to go". By definition, epoxy primers are inert, once dry. Therefore, you can finish paint them with ANY type of finish paint from ANY manufacturer, without problems.
Using a "system" of paints which are designed for use on steel will gain you NO corrosion inhibiting or paint adhesion advantages. Primers designed for use on steel will NOT adhere to aluminum as well as primers designed for use on aluminum. Most automotive primers are designed for use on steel, not aluminum.
VariPrime is designed for use on aluminum. However, it's intent is as a cheapo, cost cutting, labor saving solution. Since you have already Alodined your parts, you gain nothing by using it. The etch acid it contains will actually remove a portion of the Alodine treatment you have already applied.
Charlie Kuss