Since you already have straight pins in place, get the foam ear plugs and put them on all the remaining pins - end of problem. They are widely available at pharmacies, sold in a plastic jar. This is the brand I use:
http://www.amazon.com/Flents-Quiet-T...time+ear+plugs They have gone up in price since I got mine, but keep in mind that unlike the basting spray, you reuse these. I haven't had any wear out yet. There are similar things sold specifically for basting quilts, but I don't remember what they're called.
I have used several methods. I like spray baste, but it's costly and I have to do it outdoors because I'm sensitive to the product in the air. Our climate and the lack of a large table outdoors makes that method less satisfying for large quilts. Also, it doesn't seem environmentally friendly. I hate working with the safety pins - bother my wrist. I've found the use of long straight pins stuck into ear plugs to be a comfortable alternative.