That will not work on a giant
Thats a giant trance Kaesae.
Shhush.
the QR provides MORE than enough pressure.
choose a BIG socket thats teh appropriate size to support the outer edge, and choose a smaller one that fits through the back of the rocker, and pushes on the back of the bearing.
then take up slack in the QR by stacking sockets and other convenient implements.
do up the QR nut so that you can only move the lever a cm or so, if you try and pull it down all the way from the top it wont work.
little pushes with maximum leverage
to fit the new bearings without borking them, use an OLD bearing as a pressing surface, being a bit careful not to press it in so that it fits itself in on top of the new one permenantly.
here I have used an old, snapped, axel from a deore hub, and used the cone, pushing on the inside of the old axel, with a 21mm socket (zocchi top cap size) supporting the frame.
for some more “tool abuse”
this is a 24mm socket at the bottom, and an old spanner at the top, fitting a headset a bit less glamorously than i would have hoped
but it worked.