Alright, so there are ways to get into the ACP, but it's not worth the effort. If you do want to break into the ACP, brute force is NOT the way in. Brute force will leave server logs and will strain their server (if you do it incorrectly) so they'll know something is going on (and probably ban your IP). Your best bet will be SQL Injection (if they use a database and are dumb enough to not clean the db inputs) otherwise, backdooring is probably your only other way to get in (I'm sure they didn't secure all their ports).
If I could, so I sent a message with your tricks, like hacked ACP