After evaporating off your alcohol, it is easy to get cannabis oil out of a flask. Well, it is if you have a large flask with a big opening. What if you do not have a large flask? You likely get out what you can, and just put the next batch of alcohol in with what is stuck to the walls.
If you invested in a rotary evaporator, which allows you to reclaim your alcohol, you likely have a small flask. Heidolph offers a flask that clamps and seals the body to the neck. The body is similar to a 800 ml Mason jar with an almost 4" opening. You can easily fit your hand inside. I like to call this flask the "Big Mouth". Increase productivity, and reduce stress, with a Big Mouth, and simple scraping tools from any store's kitchen department.