This might come in handy for other people starting developing their own film. Together with using de-ionized or distilled water in the last few washes, this solved all my problems with “spotty” negatives!
I was having big issues with dust on my negatives, the often recommended and repeated solution of running the shower in the bathroom for a few minutes and then hanging the negatives in the steam-filled bathroom didn’t solve the problem at all for me: every negative was just covered in white specks. I did wonder whether the people recommending that were actually having problems with dust or just repeating something they had read once on the Web and thought it made sense.
In the end I decided to buy a cheap IKEA Billy bookcase with glass door and put some hooks in the top and cut a large hole in the middle shelf to allow it to be used for 35mm film as well. I attached some clothespins to the hooks and glued some felt around the inside of the door to keep even more dust out.
Solved my problem for a very decent price!