Technique for the plunge?

I've used the AP a few times with the Prismo flow cap and a paper filter that came with the AP. I grind somewhat coarse with my K-Plus and follow the Hoffmann recipe. Maybe I have to watch more videos but can't seem to get the plunge right where it doesn't leak a little through the sides.

How slow or fast should I be plunging? I have the clear AP so maybe only a little at a time while keeping an eye out for going too fast? It seems like there's alot of resistance. The Hoffmann recipe calls for the plunge to take place in 30 seconds but I find that doing so in that time frame would cause leakage because too fast and too much resistance.

Should I grind coarser? Is the paper filter the issue and I should use Fellows metal filter?