The key to chainsaw carving, or any carving, is breaking it down into sections. A carving is just a series of subtractions. Each subtraction you want to get more detailed. So start with basic blocking out, then you can start chipping away at features. Remember, it's the subtraction business, not addition business. You can fix some overcuts, but it's easier just to blend them in.
The tools used are two basic chainsaws.
A Husqvarna 455 with I think a 28" bar. This is a large bar, about the biggest I would recommend on that size saw
A Husqvarna 240e with an 18" bar and a 14" carving bar (dime tip)
On these basic bears, you can get away without the carving bar. It's basically just nice lights to get detail work, fur, etc... and with the 240e it's really easy to switch out bars and chains
An angle grinder with some sanding discs
A flap disc, wire brush and a drill
For finishing, I burned it with my tiger/roofing torch for the black parts, and sealed it all with a semi-transparant stain I had leftover.
This was about my 3rd attempt at a bear. The log was sourced off the side of the road that had fallen during a storm. It's about 26" in diameter I think. The more log you have, the easier this is. When you're trying to get the most bear out of a small log, you need to be more precise with your cuts and it leaves a lot less room for error.
If there is interest in this, I can do some more detailed instructions on this and other carvings. I'm far from an expert, or even good. But I enjoy doing it when the time permits.
Remember, safety first!
Glasses are a must. I use a face shield when starting out because there is a lot of chips.
I just wear insulated coveralls in the winter. but if you're wearing jeans. I highly suggest wearing chainsaw chaps or pants. They have stranding in them, so if the chain catches, it snags the stranding and slows the chain and won't cut you. A chainsaw will cut through jeans before you even know it's touching you. Chainsaw carving involves cutting on hands and knees, up high, etc... so don't underestimate how easy it will be to cut yourself if not careful.
Also, since chainsaw carving involves these odd, unsafe angles, be VERY cautious of kickback. This is when you're cutting near the tip of your saw, and it becomes easier to ride along the wood than cut through it. The saw will then come bouncing towards your face. Many people have been injured doing this. Chainsaw carving requires a lot of cutting near the tip of your bar where kickback is possible. IF you use a carving bar, your chances of kickback are greatly reduced. When doing plunge cuts, etc... stay out of the kickback zone