Thanks for your help guys!
I ended up using most of the advises :-)
Pulling the reamer helped keep them centered. When I used a wider vise grip it worked. The first on I used was too narrow and it just didn't work well.
I used the T handle for the ones I got easy access to and it worked perfect.
For the ones in the center I used a drill with the extension connected to the reamer and turned it slowly.

Thanks,
Motti