Our kitchen drain tends to clog up somewhere we can’t get to (it makes a sharp bend in the corner). Air pressure is a guaranteed success as long as the pressure has no other way to escape except the congested part. I use a long PVC pipe so I can access the drain directly. The pipe is filled up with water, then quickly plugged up before air can get in, the pressure applied, and – boom – the congestion is gone.
I bought this pressure gun for 10€ on amazon, it’s nothing special.