tl:dr CBD worked for me and the dog, almost miraculously for the dog. https://papaandbarkley.com is who I use. In California, they sell CBD with some THC in it. They ship CBD only (no THC) from Colorado. Do the drops, not the capsules. CBD uptake is much higher if you hold it under your tongue. It doesn't absorb well through the stomach and wastes most of it. Be careful where you buy from, hemp takes pollutants from the soil if they are there.
As BearSchlong mentioned upthread, I was giving CBD to my 15 year old dog for seizures and pain. He had a pancreatic tumor that burned up his blood sugar as soon as he finished eating and his blood sugar was chronically low. That caused seizures which made everything much worse. Ever try to raise the blood sugar of a dog that is seizing from low blood sugar? Not fun.
One day last November, he started having a severe seizure that we couldn't get back under control. I thought he was going to continue seizing until he died and if I'd been in Texas at the time, I probably couldn't have done anything about it. I was fortunately in California, so I raced to the closest dispensary and got CBD oil in a 30:1 CBD:THC ratio. As an aside, anything with more THC can be very bad, dogs don't process it well.
I squeezed a little over 1/2 a dropper onto his gums, probably ~20-25mg CBD. I smeared some honey on them too and he snapped right out of it. I gave it to him twice a day after that in peanut butter or vanilla ice cream.
The rest of the week, his seizures were increasingly weaker and less frequent. After a week, he never had another seizure again. He'd also had two knee surgeries and had pretty bad arthritis from them. The CBD visibly helped with his pain and improved his quality of life and mobility.
I had to put him down at the start of May, but CBD got me 6 more good months with him. 5 of those months were substantially better than the six that had preceded them.
I have also taken it for some pretty serious nerve pain and it helps quite a bit. It doesn't knock it out, but it noticeably dials down the intensity.
From what I've gathered looking in to it, CBD works better with small amounts of THC. This is called the entourage effect. However, the CBD only stuff that papa & barkley sell works almost as well. I've used their drops and their balms. They're expensive, but they work well. The balm is great for muscle aches and pains, but is a lot more expensive per gram of CBD than the oil. If something really hurts a lot, I put a few drops of the oil on the spot, rub it in, then apply the balm to help that set and soak in.
CBD comes in all sorts of dosages and ways to take it, so the best way to compare is to calculate out $/mg. In terms of how you absorb it, Vaping/smoking > Under tongue > absorption in stomach.