Heyyou, thanks for adding to the knowledge base. I believe Primer 94 is more than just a solvent, though you may be right about the solvent that is in it. The instructions advise to shake it well before using it. Also, when I was doing pull tests with 2" x 5" strips of CT3 I laid them out on a scrap of formica and used a paint brush to apply the primer. Some primer got on the formica around the edges, but it dried clear and wasn't sticky, so I left it. Now I can see clearly where the strips were because the primed formica collects dirt.
When I bond a seam with 9460 and primer I use blue painters' tape to mask the area of the bond while applying the primer.
Your question about the necessity for primer is a good one. My tests showed that the bond with 9460 and 9469 is significantly stronger with Primer 94. Primer also improved 9482 and 9485, but only a bit. If you don't use primer, 9482 and 9485 are a bit stronger than 9460 and 9469. For many uses 9482/9485 would be fine. 3M says that Primer 94 also increases peel strength. All my tests were for shear stresses, such as a tarp seam would be subject to.
Nice to hear that Amazon has these tapes. Compare prices to Uline.com.