I have a clay-lined masonry chimney, and I clean it myself top-down from a ladder. Square wire brush and fiberglass rods. I had installed a cleanout door low on the chimney, below the thimble leading into the house. Before brushing the chimney, I plug the thimble with a 6" thick foam rubber plug I made that fits tightly into the pipe inside the thimble, so zero dust into the house. From the cleanout door, I brush the where the thimble meets the chimney with an ordinary wire brush, but there's usually nothing there anyway. I remove the short stovepipe assembly all in one piece (from where it exits the stove to the back of the thimble), take it outside and brush it out with an ordinary wire brush, but there's usually not much in there but a thin layer of light gray dust. Been doing that once per year for 23 years. Inside wall of the chimney always comes out reasonably clean after running the brush down and up 3 times. I remove the creosote from the bottom of the chimney through the cleanout door with a shop vac. With my old VC, I used to get 0.5 to 2 gallons of creosote, depending on the health of the stove (highly variable) and dryness of the wood (somewhat variable). It will be interesting to see how much I get with the new Oslo. Judging by the clarity of the gases exiting the chimney, I'm expecting less.
For the stove itself, I always make sure my last fire of the season is a hot, small fire that never gets shut down, so that if there are any unburned deposits in the nooks and crannies from the previous overnight burn, they get converted to gray ash. After burning season is over, I shovel out all the ash I can from all the nooks and crannies, vacuum off the outside of the stove. I don't usually vacuum the stove inside, as even a HEPA vacuum cleaner might let a bit of ash dust through into the house, and it's just not worth it. With the old VC, I'd remove the cat element and vacuum it out very gently, and inspect the (usually somewhat deteriorated) refractory housing in the back of the stove, gently vacuuming out any loose fragments or ash that fell to the bottom. With the new Oslo, none of that applies, but I imagine I'll remove either the oval cover in the top or maybe the entire top of the stove, and gently clean the insulating blanket on top of the baffle, if needed.