Try a homemade slosher Scroll down to my post to see a picture. Your fingers never touch the negs, except from film holder to tray. 450-500 ml of developer will do 1-4 sheets and ensures adequate amount of developer.
Is that because when its fully loaded there isn't enough room for the liquid to move around?
It seems there isn't enough spacing between the slots, but even with slots only half loaded it lacked decent agitation patterns. I seem to remember a professor calling the effect bromide drag, but I'm not sure that was technically true. I got streaks on everything, especially evident in skies and on walls.
That I evolved a technique that kind-of worked with the yankee seems to be uncommon. Even with only haf the slots loaded I had to slosh it around so much that considerable diluted developer leaked out. It worked, but was a poor solution and I would not use one again. I sort of pushed and pulled it inside of a tray until it just barely lost any fluid with it a certain amount full.
I was a dedicated devotee and defender of Yankee tanks. Must be because I was born in the northern US. Anyway, after so many people complaining about the uneven development in sky or other even toned areas, I finally noticed it in my negatives. I don't often include skies in my compositions so it wasn't obvious. Since then I have tried every possible kind of agitation to eliminate or at least reduce the uneven development. Sometimes I would succeed, other times fail. Sometimes I would succeed and then fail on the next attempt using the same strategy. I have decided that for me, the tanks are inconsistent and unreliable, which is unacceptable to me. So I am returning to open tray development. Yes, I have to work in total darkness, but I actually don't mind it as much as I used to, especially since the developer I am now using is pretty fast. And there is something to be said for sitting in absolute darkness and working by the sense of touch for 15 minutes or so.