I was wondering why I had ants on my plants earlier in the year. Seems they collect the aphid's 'honey dew'. Used the soap-oil-water mixture on them and got rid of them. I am hesitant to spray the buds now as said you leave a residue, mind you I also dunk the harvested portions in a water hydrogen peroxide mix. The soap should remove the canola oil when dunked but I rather hose off the buds. I have also used a 1" fine paint brush to brush the bugs off the underside of the leaves. Was nice to see earlier a bunch of lady bugs munching away on my plants. Wonder how to call them back?
Yup, not just collect the honey dew, they offer protection and all sorts... They literally farm aphids.
OP: I'd recommend the same as xtsho already stated, a heavy blast of plain water would be fine, your aim is to knock them off the plant IIRC because they cant climb back up, So water works fine especially in veg when you can just blast everything with the hose.. But for week 6 and depending how big your buds are, I would just use a stream on a spray bottle, You may even be able to add a bit of 3% peroxide if you're dealing with any PM too, 2 birds, since thats mostly water too and will only need to soak the buds once.
As for the ants when you see them all over the place, DE works great but if it gets wet outdoors it loses its effectiveness I think, so I put out small bowls filled with 1 part canola oil and 1 part soy sauce... Do this during the summer veg near all my plants and Ill put them out at 5pm then check on them the next morning at 6am and the bowls would have hundreds of ants in there, dump out and refill as needed and it helps keep the population down. Used as one small part of an overall IPM/integrated pest management system such as beneficial plantings to attract beneficial insects, bugs, bacteria and fungi. Sticky traps, DE, B.t., etc.