using agent to accumlate post in agentized groups

[hput]

I once had some working knowledge of using gnus agent.  But it leaked
away over the last 20 and more yrs. As it became faster and faster to
get news.

I want to acquire several thousand messages from certain groups.

Ones that likely carry info I most want to access.  So back then I used to
download Thousands of old messages overtime so as not to bog down any
servers.

I lost all my old thousands of messages over many host changes, moves
and fool blunders.

My aim then and now is to subject the messages to my own regular
expression searches for bits of code and the like.  Not so easily done
on google with its inability to be made to look for much detail, as of
course is required due to the massive, massive amount of stuff it
searches. 

Whereas say some 200,000 posts can be regex searched and although slow,
the sky is the limit on detailed searches. regular expressions are
endlessly customizable to dig what you want.

-------       -------       ---=---       -------       ------- 

So Can any one provide a step thru to getting started accumulating
messages with the agent?

I used a `true' predicate back when I was working on it, but don't
recall much other detail.

And of course a lot of the needed information is in larsi (and many
others) efforts in the gnus manual.  But combining into a working
setup is another animal.  So hoping someone who uses the agent
regularly will be willing to coach me a little