Or if it is just 2 PCs, REMOTE BUFFERS will work well if they are network connected.
To set up remote buffers, set up the primary update PC to crack as usual to whichever proxy server/keyserver you would fetch/flush to.
On the second PC, go into the config options, disable fetch/flush from keyserver, and enable fetch/flush from Remote Buffers. Specify the folder on the Primary PC that contains the buff-in and buff-out files. Maintain buff-in and buff-out files on the second PC, enough in-buffers to last several days incase of network problems.
When the second PC needs blocks it will retrieve them from the Primary PC, and when the Primary PCs in buffer gets low, it will fetch from the team proxy or keyservers.
Running your own pproxy will work too.