Hope this helps others finish out their grinds.
Pretty straight forward - enter UBRS, first 'main' room with the offshootrooms (their are 6 or so) each containing one Blackrock Summoner - kill the mobs, leave the summoners - they will continue to summon mobs worth 15 rep per kill. 15 rep x6 (or more) summoners + infinite respawn which are easily downed.Hope this helps.