Use a telescoping painters handle with a piece of wood taped to the end. Notch the wood portion to accept the baffle, and use the telescoping handle as an extension of your arm.
Best bet is if you have someone to ‘reload’ the baffles so all you have to do is work the center and pivot back and forth from the center area to the person reloading the baffles. Lessens the chance of a follow up project on teh ceiling below…
If the baffle doesn’t want to release from the pole after you finesse it into the eave area, give the pole a twist and break a little piece away to release it, assuming you are using foam baffles. My assumption is that you are talking 24 oc with the truss construction? You might be able to get away with every 2nd one.
Easier with 16 oc, but still doable.