Yes I have. I now have on most of mine after previously having a Sony A7III that got a big rub mark when I was just carrying the camera round the zoo.
It you put the skins on from from your camera/lens being new, it basically means your camera / lens then pretty much look like new if ever come to sell them. I've had a camera / lens that I've since sold and taken the skins off and pretty much means they look like you've not used them.
I've mostly used a seller on eBay - similar prices to the link you've posted. However they didn't have some I wanted and also now seem to not do them anymore, so I've actually used some from Aliexpress recently. They are about half the price on there and just the same quality. The Sony A7c ii for example I paid around £15 delivered for vs £38 (inc delivery) on the link you've posted.
They are fairly easy to put on. Normally they'll provide you with some plastic tweezers that help with the fiddly bits. Getting them on the camera grip part I find the most difficult, but find using a hairdryer once you've put the skin on helps with this. Also its a lot easier if you put on in the numbered order - they basically are like stickers in lots of different parts and are numbered in the order you should put them on.