Bogofilter training

[jyry at helzinki.net]

Hello,

I just abandoned SpamAssassin in the hope that I could find help with bogofilter.
I have been considering the following method based on what I have read.

1. Messages are filtered and sorted into INBOX and INBOX.Spam accordingly.
2. Users check INBOX and INBOX.Spam and moves/copies false-positives and
false-negatives into INBOX.NotSpam and INBOX.IsSpam accordingly.
3. Bogofilter is learns from the messages in the INBOX.NotSpam and 
INBOX.IsSpam.

I have a few questions about the above:
-Is cron the only method to let bogofilter train from the messages in 
INBOX.NotSpam and INBOX.IsSpam?
-Should I use a site-wide dictionary or one per user?

Point out any mistakes and please suggest better methods if there are any.

-Jyry Suuntala