Yes, Grey Crack Stix is paintable.
You will need a propane torch to heat the rope. It then spreads into the cracks and seals. Yes it hardens on its own. A very good product.
If you can dry the area completely for the time that you apply it and 15 minutes of hardening time, you will probably be OK. However, moisture at the time of application will prevent the material from melting and filling in as it should.
I used polymer paver sand because I had some very deep cracks (expansion joints). Regular sand would have kept on going down. Pour it into the cracks, brush all the loose sand away, then spray gently with water and let set, then let dry completely. It sets up pretty solid, even with 1/2" cracks. I had 450' of cracks to fill. About using regular sand- I tried that first, had problems. The torch wants to blow the loose sand all over the place. As the stix melt, the sand starts sticking to them and the stix start writhing around like an earthworm. You are supposed to use "high temp" backer rod. Good luck finding it! The smallest lot I could find was 2300', most places offered 5000' and up. HD does not carry it, and no one I asked even knew what I was talking about.
You are correct. Same product different sizes.
No, it's intended for horizontal surfaces only. (You melt it into place with a blowtorch.) When filling the small gap between a concrete porch and my brick home, for the vertical parts of the steps I used a premium poly "caulk" that's often recomended for joining/sealing 2-piece stone window sills. It's works for vertical and horizontal joints, and is available in 2 colors - limestone and concrete (gray) that matched this product pretty well. I can't think of the brand off hand, but it's in a yellow tube.
No way. This is quite thick and tough to cut linearly. I also used the thinner product, smashed it with a hammer flat and cut for thin cracks, bit 1/8 is really thin so it will be a challege to make that work.
This material is closer to actual plastic as opposed to the crack filler you use from a tube. In this case acid wash and stain does not adhere to plastic as well as the other material. To compensate for this, I have left a small gap between the top of the pli-stix material and the top of the crack, thus leaving me room to add traditional crack filler on top to allow for acid wash or stain.