I have 2 toolheads for my 650: I have the RT1200 b and a RCBS decapping/FL resizer (at the 1st station) on one and the dillon dies (along with another FL sizer on the first station as well) on the other.
The process (for me at least) is simple: They all get trimmed the first time. I put them through the case feeder and have my 1st toolhead installed. I just work that lever until they've all gone through. The trimmer will only trim the ones that need it (after you set it for the correct length); everything gets resized/deprimed anyways.
I then dump the cases back into the casefeeder, change tool heads to the one with the 3 dies and my low powder sensor, and get down to loading.
It might sound complex, but in reality, it just comes down to working the lever twice, as the toolheads are already set up and all I have to do is switch them out. I only have to trim the batch once as well.
The reason I don't trim the cases again after doing this is because; 1) the reloads only get fired in my rifle, so they get fireformed to my chamber, and 2) I toss them after 4-6 reloads anyways, which is usually not enough time for the neck to stretch back to out of spec lengths.