Firstly, I too am no expert when it comes to film development, so I can only speak as I find (or write as it is here)
Some years back I had a problem with crud on my negatives. I went through a process of elimination to get rid of the problem. The problem turned out to be my water supply, yet, before arriving at this conclusion, one of the things that I picked up on here on APUG, was that when re-using fixer, you are subjecting your film to a fluid that is full of silver particles. Now, the way I see it, if my film emulsion is soft enough to hold on to a lump of lime from my water supply, so much so that it takes a good scrape with a cotton bud to clean it, and even then sometimes it will not budge, then I am sure that the same emulsion is quite capable of holding on to all that silver floating about in the used fixer. I prefer that my film sits in a clean change of chemicals throughout the development process.
My method may be a bit extravagant but my film is always squeeky clean now, and I usually only have to pick of the occasional fleck of dust with the tip of a brush.