You can express all of the liquid (colostrom) that you have two times a day and your body will continue to produce. If you decide to pump to stimulate some labor

I wouldn't bother storing it, unless you believe you have a problem nipple (inverted) or if you are finding you have a plugged milk duct or some other issue that may interfere with your breastfeeding immediately.
You will ONLY start to produce actual milk when the placenta is no longer attached to your body. The progesterone that has been produced by the corpeus luteum (from ovulation) up to 14 weeks, and then produced by the placenta since then is what is 'delaying' prolactin production. Prolactin is the hormone that will kick start milk production. When progesterone levels fall after the birth of the placenta, Prolactin production will go into overdrive.
Wait 24-72 hours and bam. Instant dairy.
Colostrom will give baby antibodies and help make their digestive system ready for mama's milk.
The 'hardness' you describe is the production of the colostrom as you get closer and closer to the end. I have noticed, I'm much more 'full' now during the day and during my evening showers I let down and express enough to make the ladies more comfortable

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I've heard the added nipple stimulation (which helps labor along if timing is right) can also help to 'toughen' the skin around the nipple so getting baby latched and used to breastfeeding isn't quite so painful. (The equivalent of perenial stretching exercises). So, yah I've been doing that too.
One thing to be aware of too is that milk/colostrum can take on the "color" of foods you eat. I went crazy on beets a while back, and the color spilled over into my urine AND my milk. So if you notice a wonky coloration to your breast milk/ colostrum think to see if you've had high color foods... beets, carrots etc.