You might want to read through the hundreds or SVB squash vine borer discussions here for more realistic information about how to deal with them than what you have planned. Most sprays, even commercial pesticides, are not effective so your insecticidal soap would be a waste of time and effort.

The moths have to be prevented from access to the plants to lay their eggs - row covers are recommended for that. Once the eggs are laid you have to physically remove them as once the larvae hatches and immediately bores into the stem no spray will even come into contact with it.

Dave

Here is a link that might be useful: SVB discussions

I have two new strategies I'm trying this year. I did row covers last year. They worked, but were kind of a PIA.

Firstly, I'm painting the leading vines with Sevin. That way, the Sevin doesn't get everywhere. Not on the leaves, flowers, or fruit. Just on the vines that the SVBs are trying to penetrate. Just the leading vines. Not the leaf stems. I don't care if they kill a leaf. Takes about fifteen minutes every two weeks to do this, though when the vines are tangled, it gets a bit confusing. A cheap one-inch paint brush works great. I suppose a sprayer with a narrow spray head would work as well.

Secondly, I'm mounding dead leaves and mulch on the vines. The leaves stick up out of the mulch. If you bury the vines, the SVBs can't find them. If the vines root, so much the better. Of course, at the end of the season, you just dig the mulch in. Now, this is for vining squash. Might not work as well with upright squash.

So far so good. No SVB damage seen.

I did what Dan is doing last year, and 50% of the plants survived. I also slitted open plants that stopped producing, although between the borer and the slit they survived but never produced much after that. Still, it is a problem to give away all those zucchinis in late July and August.