Charles
The only reason I suggest doing that is because its quick and easy to see how an email was scored by spam assassin while you are getting used to how it scores junkmail.
You do not have to do this, you can just look at the email headers and Spam Assassin writes the score in there as well. I just think it saves a few clicks if you rewrite the subject lines and it is right there in front of you for speedy reference.
Once you are comfortable with how it scored you and adjust X up our down to the point where spam assassin with actually do something useful with emails flagged as spam.
When you like the numbers go into cPanel > mail > filters and there is a spam assassin hint which works well to discard email tagged as spam so you never see it, or, you can forward it to another email box instead of "Discard" if you want to manually process / check forwarded emails marked as spam for false positives.
I have had better luck with the filter previously described versus using the one you are talking about, either SHOULD work, I know the filter I discussed DOES work. haven't tried the one on the Spam Assassin page in a while though, at one point I know it was not properly discarding email.