Should I use oil or grease in the pro qualifier lube port?

Grease. It is there so you can apply it to the main gear and keep it and the pinion lubed without having to take the side plate off. However I find that after the yearly service I give mine I don't have to put any more grease on the gears.

X2 the rare occasion I do add I rotate the handle I few times and then use a Q tip to remove any excess