That citrus spray sounds interesting to me too. I always have orange peels in the freezer because I save them for steeping with tea and baking. Hmm. I'm wondering if I couldn't just make up some of that orange water, strain it and store it in the freezer. The soap could be added when you are ready to use it.
Also I heard that you take 2 water bottles and cut the bottoms off. You notch out a piece about 1/4-1/2 inch across and from the top making a u shape cut out. Do this on opposite sides to both. Then staple together where the two ends make a hole and fill with a dark beer. The snails and slugs love it more than your plants! I'll post a pic soon on how it looks if this sounds confusing.
That grits idea is quite intriguing. Would this really kill the whole nest, or just cut down the numbers for a time? A few years back I purchased some citrus pest spray, and it worked extremely well to deter ants. I've been looking to buy more, but I can not find it anywhere. I should probably stop wasting time looking for it, and start making some using the recipes in this thread.
Try planting mint around the perimeter of your greenhouse or planting area. Ants do not like it and you can make a yummy tea.
The problem I have heard with mint is if in the ground it must be contained or it will take over your entire garden. So it that is the case you MUST plant a box of sorts all the way around the garden so the roots can not spread. Please correct me if I'm wrong.