I did mine yesterday. It wasn't painful, but was a bit fiddly. I'm glad I don't have to do that regularly.
I didn't watch the video but I did read the instructions carefully. I used my ring finger on my non-dominant hand, and aimed for the side rather than the fingertip.
My finger started bleeding when I told it to: the blood dripped out easily (a drop every few seconds) and I was able to fill to the 600 line. A couple of drops ended up on the outside of the rim of the tube, and when I pushed the lid on it spattered slightly on the cardboard holder 🤦♀️ I wiped it off but it left a faint stain.
My finger also stopped bleeding when I told it to, although I did use pressure and elevation before handing the job over to the rather underqualified plaster they provided.
Our priority postbox has a 5pm collection, so I did the test at 4pm and posted it at 4:30 so it wouldn't be sitting there through a hot afternoon.
I had suspected Covid fifteen months ago, but at that point testing was only available in hospitals and care homes. I've had both doses of the vaccine, but not sure if the antibodies from that would show up on this test.