I thought I would write this up as a little HOWTO on using the SpamAssassin-recommended approach without having to use RulesDuJour at all.

Firstly disable RulesDuJour
   chmod -x /etc/cron/daily/rules_du_jour_wrapper
Now it won't run every night.

Next, delete all the rulesets downloaded by RulesDuJour, as we're going to use sa-update to get them instead. We don't want 2 copies of the rulesets.
   rm -f /etc/mail/spamassassin/*sare*cf
   rm -rf /etc/mail/spamassassin/RulesDuJour

Create a file for your list of SpamAssassin 'channels' including the default set. Attached is a file to drop into /etc/mail/spamassassin/jkf-channel-list.txt. Note that this is my *personal* set of SARE rules that I use on my servers. I strongly advise you go to www.rulesemporium.com and read the descriptions of all the rulesets and adapt the file to your own personal requirements.

Next we need to add a PGP key to SpamAssassin's update method. This is a condensed version of http://daryl.dostech.ca/sa-update/sare/sare-sa-update-howto.txt.
   wget http://daryl.dostech.ca/sa-update/sare/GPG.KEY
   sa-update --import GPG.KEY

Next we need to add some command-line arguments to the call to sa-update.

If you are using MailScanner 4.62.2 or later (which I'm just about to publish) then edit /etc/sysconfig/MailScanner and edit the definition of SAUPDATEARGS to say
SAUPDATEARGS="-D --channelfile /etc/mail/spamassassin/jkf-channel-list.txt --gpgkey 856AA88A"
(That should all be on one line of course)
Once you are happy everything is working, remove the "-D" and it will run a lot more quietly.

If you are using MailScanner 4.62.1 or earlier, then edit /etc/cron.daily/sa-update and/or /etc/cron.daily/update_spamassassin and/or /usr/sbin/update_spamassassin to make sure the call to $SAUPDATE says this:
$SAUPDATE -D --channelfile /etc/mail/spamassassin/jkf-channel-list.txt --gpgkey 856AA88A
(That should all be on one line of course)
Once you are happy everything is working, remove the "-D" and it will run a lot more quietly.

That concludes the main bit of this.

However, there is one extra ruleset which you might like to try. I've got it going and it appears to work pretty well. Attached to this message is a file KAM.cf.sh which you should put into /etc/cron.daily/KAM.cf.sh and make it executable:
   chmod +x /etc/cron.daily/KAM.cf.sh
Run it once to get the initial copy of the ruleset file. It will keep a backup copy of the KAM.cf ruleset in KAM.cf.backup, which it will use if it can't download KAM.cf correctly later.

That's about it.
I hope this improves the effectiveness of your spam checking.

Jules