The on-loan Leicester striker pounced twice in nine second-half minutes to send the Cumbrians home empty-handed ahead of their Johnstone’s Paint Trophy clash next Sunday.
His first came on 74 minutes when he latched onto a half-cleared ball to slot home from 12 yards before, minutes later, he was in the right place to seize on a goalmouth melee to bury the loose ball from close range.
Defender Lubomir Michalik gave the visitors hope with minutes remaining when he hammered a free-kick into the bottom-right corner after Brentford defender Leon Legge was lucky to only see yellow after bringing down striker Roy Loy.
It was harsh on Carlisle, who had the better of the chances in the first half, with Craig Curran and Ben Marshall both seeing efforts blocked by rookie keeper Simon Moore or cleared off the line by Pim Balkestein.
Harry Arter also went close for Carlisle after the break but Brentford looked threatening on the counterattack, with Schlupp and Myles Weston both a danger.