You generally cannot grease sealed bearings. I would not soak the bearing assembly because you could wash out the lubricant.
Use a solvent, like white spirit or paraffin (thats kerosene in UK English, right?), and wipe off any grit, then scrub all the threads on the bearing assembly and BB until they are perfectly clean. Liberally grease on re-assembly.
Il faut de l'audace, encore de l'audace, toujours de l'audace
1980 3Rensho-- 1975 Raleigh Sprite 3spd
1990s Raleigh M20 MTB--2007 Windsor Hour (track)
1988 Ducati 750 F1