shouldnt be that difficult, but you need to identify yourself to the ground staff and show them your crew id as well, unless it is a training flight and all the crew jumpseats are occupied most of the time the Captains will oblige your request if you positively identify yourself as airline crew.
EBB to NBO loads are high for most part of the year, you might want to travel midweek if you can, chances are higher than on weekends
Good Luck