Never used a blender for this (and I will take a notice, tho I would afraid doing this: my guess it will go strictly against the instructions ). I think the best option would go and buy a pack of a ready-made ground coffee ☘️ At least once I found myself in a situation when my 1st Siemens electric grinder (it was doing the job since 1998! maybe even earlier), I momentarily ordered a new one, same model. Of course, I easily can imagine when it is not an option, be it lack of money or location where you simply dont have access to the market goods. Just imagine that you were teleported back to XIX century and found yourself with a pack of beans and without electricity... in such circumstances your favourite electric grinder really would be out of hand. 😳
So, speaking about my personal experience: once I visited my friend who always obtain ground coffee, but she was presented a pack of beans as a birthday gift exactly on that day, there was a big company, all claimed they wanted to test the gift - and there was no electric grinder in the house at all. But, my friend is very fond of vintage stuff, she visited Holland many times and paid a proper attention to the local flea markets - she have got a lot of cool stuff there, including this traditional manual grinder. This one wasnt too old, but it is exactly the same model, as they used in XIX century.
So, I had a fat chance to practice in using this gadget. Also note: I had to grind beans for a big company, not for a self doze. Of course, I don't remember in details how that coffee have tasted, but here's what I remember for sure: the coffee grinder provided a very coarse grind, delivering grains of 0.6-1 mm, but the grinding speed was even worse. I turned the handle on and on and ground for 20-30 minutes (it did not feel like fun!), and it was then that doubts took root in my mind, that manual grinding is no good. Yes, perhaps it was a great option a hundred years ago, when people had a different pace of life, but not now. Said friend told me about another personal case - this is not my experience, but I think it is worth retelling here for everyone.
A situation may happen in your life (nuclear war? hurricane? or a trivial 3-day emergency blackout), when you cannot use your electric coffee grinder, and a manual coffee grinder was not purchased in advance. Given the beans and the desire to drink coffee no matter what - what will you do? what can be done? My friend in this situation used a rolling pin. Having laid the beans out on the table, she covered them with a cloth and rolled a rolling pin over beans getting coarsely ground coffee quite quickly. I can't say how much effort it took her (it can be quite subjective)... So a rolling pin is a very useful and multifunctional item that definitely should be kept in every household!
I wish you had a great coffee everyday, my dear friends 😍