I am asked this question so many times I decided to post this on my blog. Hopefully dyers out there searching the web will find this information useful. You can see some of the pics, either above or below this posting of what I'm talking about.
You can perform multiple dye extractions with cochineal bugs. What I did for this demo was to weigh out two ounces of the bugs, cover them in water, then heat them to near boiling. I then turn off the heat and let them sit overnight, in the same pan. (one these days I need to buy another one of these pans as it is my favorite).
Day two I strain the bugs in a hand held sieve, into a much bigger stainless steel pan (about 8 quarts I guess). I then place the bugs back into my smaller pan, cover with water and reheat them to near boiling. I then turn off the heat and let them sit overnight. The next day I strain them again, placing the dye liquor into the previous days extraction. I repeat this process upwards of 20 times.
You will need to heat the dye liquor every few days or so to prevent mold from forming on the dye extractant. When you are done it will be blackish in color. This dye liquor is a super concentrated cochineal dye bath.
When you are ready to dye just remove a smallish amount, about one quarters cup worth, from the dye liquor and place it into your dye bath water. If it's still blackish just add a smidge of Alum and it'll redden right up. I do this all of the time.
This is an excellent way to get the most bang for your dye resources. I do this all of the time with cochineal and other dye materials. Most dye materials lend themselves to only one or two extractions, beyond the original dye extraction.
Wood chips however can be pushed, Osage Orange is one such woody material. I soak it upwards of 3-4 weeks before I use it as my dyebath. I then take my chips and lay them out in a thin layer, so they don't get moldy, and dry them out. Once thoroughly dried they can be resoaked for a lighter dye extraction.
Also it should be noted that most woody dye material colors are extracted better if the dye materials are soaked in pure alcohol. I use Everclear for the best results. Dye materials that are fugative, such as Alkanet, are less inclined to fade if they are soaked in alcohol first.
You could use wood alcohol but it tends to make protien fibers brittle, and the colors are not as brillaint. You could also use 90 proof Vodka, but again the colors are not as brilliant.
You don't need much Everclear to extract the dye color from the woody materials, just enough to cover the chips or sawdust.