So the Ilford sheet gives times, but tells you to use the Ilford 4x in 10s/min agitation
OTOH: I've heard that Fuji Neopan should be agitated 30s to start, and then 5x in 5s/min
So the Ilford sheet gives times, but tells you to use the Ilford 4x in 10s/min agitation
OTOH: I've heard that Fuji Neopan should be agitated 30s to start, and then 5x in 5s/min
I doubt it will make much difference how you agitate, as long as it's every minute.
If it were me I'd follow the instructions on the Ilford data sheet, use that as a base, and adjust developing time / agitation as necessary.
Just changing developing time will change the slope of the film curve, while changing agitation will change the shape of the curve. To change the shape of the curve in any meaningful way, you have to make more drastic changes to agitation than what you mentioned above, like 10s every 3 minutes, for example.
First agitation IS important. If you agitate too much and too long you get surge marks from the developer rushing through the sprocket holes. If you agitate too little you get unevenly processed negs.
I have found 30s with gentle full inversions does the trick. And don't fill the tank completely; just cover the reels and leave only a small air pocket on top. If you fill the tank completely, the developer doesn't move around when you agitate, and too little developer causes the developer to travel at high velocity.