IF (big IF) your 2WD bearings look good when it's time to change rotors...clean and repack the original bearings, put them in the new rotors, and don't obsess.
The new rotors should have new races already installed. If the old races aren't burnt, pitted, or otherwise ruined; and if the rollers themselves look good...swap the old bearings into the new rotors with the new races. New grease seal. And let 'er rip.
I would NOT do this if there were any indication of bearing failure.
For the record, what's sold as the Gearwrench bearing packer is a TERRIFIC tool. They used to be made by a small, independent company. They were also knocked-off by Lisle who has a very similar product. Anyway,
very recommended for packing bearings IF you put a paper towel over the tool before you step on it to squeeze the grease into the bearings. Otherwise the dirt from your shoe goes into the grease. Stack the smaller, outer bearing on top of the bigger, inner bearing. Put the tool's plastic cone on the top, step on it to fill the space between the bearing rollers. Takes about seven seconds to pack both bearings from start to finish.
xc_hide_links_from_guests_guests_error_hide_media
www.amazon.com/GearWrench-2775D-Hand-Bearing-Packer/dp/B0002NYDYE/ref=sr_1_3?dchild=1&keywords=EZ+Squeeze+grease&qid=1629479188&sr=8-3