Hard to say for sure, but I my first
guess would be that water may be getting mixed in with the 303. I've experienced streaking with every product I've tried due to that. Now after I wash/dry, I'll let the VX sit for at least several hours before applying 303 - if it's cool outside, I'll even let it air dry overnight or for a day or two. This insures all the water evaporates out of the pesky recessed areas/cladding screws, etc.
Also, if you're using 3 microfiber towels for application, you may be wasting a lot of 303. I apply it with one 3"x3" to 4"x4" section of cloth cut out of bigger rags, old clothes, whatever is handy. Then I remove the excess with one of my old bath towels that has been relegated to "garage duty." Here's my full method:
* Wash/dry VX
* Let it sit & air dry completely
* Wipe off dust with a slightly damp terrycloth towel (if I let it dry for more than a few hours)
* Drench a small rag with 303 and apply liberally to one section (see below).
* While the rag is still damp, go over that section again to help even it out.
* Wait a few minutes and thoroughly buff off the 303 with a clean, dry terrycloth towel.
* Go to next section
I split up the cladding into 5 sections: entire right side, entire left side, front cladding, rear cladding, and finally half moon/door handles/etc.
The small applicator rag may look dirty as it cleans off places you missed during washing. Ignore it, it will still work out fine.
This has worked great and has consistently given me good results.