I've compressed snapshot files into cab files letting the snapshot agent to do it, but also didn't compress the snapshot and then manually compressed all the snapshot files with rar or any other program.
The difference was very little but manage to compressed it a bit more manually.
If the snapshot is too big and you can't send it across your link, then you can save it to a Cd and have it mail to you.
Or you can also, manually export the tables, (one by one if necesary) to single text files, send those compressed txt files, and afet you sincronized all your tables, you can subscriber without creating the snapshot.
But you will have to deny any changes during this process.