Quite easily I managed to use a pretrained resnet to do some quite astonishing things on completely unrelated pictures we have. And it only took like 10 epochs at ~4 seconds each, so less than a minute of training and it was already quite good.
What I did was that we have taken pictures of things during a process. At that point, I know what the volume should be. So used ~thousand of those images to train a regression model to estimate volume of the thing in the image.
Then I run the model on other images and compare what the model thinks is the volume compared to what it should be. When it's off, the algorithm is mostly correct and we have an error on our side.
Quite astonished about how quick and easy this was to do with the high level api of fastai. Took me 2-3 days.