I still use my BB30 generic one for around $20 I bought off the bay a few years ago to press my PF86. I just turn the cup around because the diameter is obviously too big for GXP, and use the flat part, just be real careful to press one cup at a time, not both simultaneously.
Works like charm.
I also did basically the same thing for wheel bearings as well, just a bolt, some washers/nuts, used some bearings drift press that do fit into the holes properly...just a wrench on both side and slowly work them in.
If I was a pro mech, yeah, I would buy a $200+ bearing press/drift set for bearings to do this...same for BBs, but since I do it maybe once/twice a year, not worth it.
I did buy proper drift sizes for removing bearings though for wheels/BB. Then use sockets/extensions for hammering the other side, works fine. They are relatively cheap, you likely only need like 4 of those for all of your bearings for under $60. Basically I've got like $80 in parts for all the bearings I need to handle.
This is a shot of the entire set I use for everything. Like I said, not shown is the socket/ratchet extension I use to pound out the drift with a rubber mallet.