One way is:
1. Import first in lossless.
2. Change the import settings for a lower bitrates.
3. Right-click on your songs and select "create MP3 version" (or whatever the format you choose).
4. Itunes will create a copy.
5. Rename the album of the new tracks from "Regina Specktor" to "Regina Specktor (ipod)"
6. Create a "smart playlist" called iPod for all "albums" contains "(ipod)"
7. Select "manualy sync" when syncing your iPod and select the "iPod" playlist.

This sounds like a lot of work, but it is actually not that bad and you do it only once.

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