The Firelight and Oslo are very simple beasts, which means there's just not too much to be done, I think. Not sure I'm an Oslo cleaning expert, having only done it once, but here are a few things I noted.
Be sure to clean out the rear of the ash pan enclosure. Ash buildup behind the pan can interfere with the ash pan door closing. I had this problem with my previous stove, which taught me good ash pan management to avoid the problem, but it could certainly be an issue with this stove as well.
Depending on your pipe arrangement and burning habits, you could get a fair amount of ash dropping onto the rear of the baffle on top of the blanket. You can't really access this to vacuum it from the front door of the stove very well. In my case, I'm removing the pipe anyway because of other cleaning activities specific to my installation, but if I weren't, I'd be looking into either removing the entire top of the stove, or removing that oval access plate on the top of the stove (not sure if the Firelight is exactly the same). After a year of burning, I found almost nothing dropped onto the baffle insulation blanket, so I don't think I'll need any serious cleaning in this area until a few more years go by. The top of the stove can be removed by just lifting it off after removing 3 bolts (Oslo) that hold it. Many folks have reported not bothering to replace these bolts upon reinstallation of the top, since it's heavy enough to seal without it. I haven't done this yet, but probably will after a couple more years. If you're trying to vacuum the top of the blanket, be careful not to tear it or move it out of position. Mine seems to be gently stuck to the baffle so it won't move, but others have talked about the blanket interfering with draft if it gets bunched up.
It's probably a good idea to remove the little "doghouse" cover in the front inside the stove, and vacuum out any ash that could interfere with the smooth sliding of the primary air control. While the cover is off, squirt some graphite powder on the sliding track to keep it running smoothly. You may have seen other folks here complain about sticking of this air control. In our case, I had to lubricate it about half way through the season, but then at the end of the season it was still smooth. So, doing a preventative lube during the annual cleaning may be enough to keep it in good shape.
