There's alot of questions I had about anchors when I took a river mooring about a year ago and decided it was time for a "proper" anchor (I got a 15kg grapnel anchor and a couple of meters of flimsy chain with the boat, definitely not enough). Bear in mind here that I have absolutely no experience using an anchor, I've just tried to follow the best advice I can find on what to have and how to use it in an emergency. Danforth is definitely the type I have usually been recommended, apparently it's a good multi tasker when it comes to digging into different surfaces, which is what you want when travelling on river. I'm still a little unsure what the ideal requirements to attach the warp (rope, from the end of your chain to the boat) to the boat are, there are scare stories about T-studs snapping under the load and some people recommend having something bolted through the steel of the hull. I don't have that, but the bollards on my boat are chunky (what I assume if a short length of 2"-3" diameter steel tube welded to the gunwhale with a little egg shaped sheet steel cap welded on top, that's what it looks like, anyway) and I hope that the scare stories I've heard are about the T-studs you see that are basically a T shape of 1"ish steel bar welded onto the gunwhale. I have been told that the correct way to deploy it is to slowly lower it by hand and wait for it to "bite" before tying the warp off at an appropriate length, not sure how easy it is to judge that process for the first time in an emergency situation so I always have the end of my warp looped over a bollard so if the worst comes to the worst and someone panics and just chucks it overboard, at least it's attached to the boat. As for recovering the anchor you've got it spot on, from what I've heard, it's all about pulling the anchor in the opposite direction that the boat was pulling it in the wind/current. The other thing you need to bear in mind is the total length of your warp+chain combined, I've been told that you want 6 times the maximum depth of the water you're in, which I believe can vary quite a bit river to river. For the Avon (as far as Bristol, not into the channel) I have been told that over 25m is ideal, so I've ended up with 17m of rope and 13m of chain. A friend who is setting off from Bristol to Sharpness soon was recommended quite a bit more, I believe they've ended up with 30m of rope and and 10m of chain, but it might be even more than that.