Aye but killing more than one bs in the same system within a 15 minute period is pointless

if you stay in one system you have to kill a bs, wait 10 - 15 minutes, kill another one, wait 10 - 15 minutes kill another to get the sec increase. You can kill as many BS in 15 minutes as you like, it only takes the highest value BS and works out 1 security gain.
If you kill the highest value BS in one system, then move onto another system the overall timer resets, kill another high value BS, move onto a new system, kill a BS etc. that way I have been able to get 5 or 6 increases in 20 minutes or so.
Also if you re-visit a system within the 10 minutes it appears as though the system timer doesn't reset so you need to figure a loop of system with it taking longer than 10 - 15 minutes to do a round trip to maximise the sec increase.
That's how I do it and seems to be the preffered methodm but it still takes a long time, with my social skill on lvl 4 (the one that increases sec gain with concord I'm getting on average 0.22% increase each bs I kill, with this it is taking me roughly 15 - 20 bs per 1% of sec gain iirc, I might be way off on this, and if I could be bothered I'd do the calculations to find out what the sec increase actually is on 0.22%
Either way you need to kill 1 battleship then move to a new system, I don't bother with loot unless it's a named one.
Also that thread seems to be based around ratting for profit

I'm not doing it for ISK but for sec increase, if I come to a triple 1.1 million BS spawn I'll kill one then move on, when I come round again the last two will be there so I kill another, etc. eventually you can get to a stage where the time you take to do a round trip lets the bs's respawn and so you can go for a fair while not needing to explore the other belts.
That's an hour of doing my method, by doing the 15 minute thing you'd only get 1 sec increase every 15 minutes, which is 4 per hour

this way allows you to nearly double the sec gain. In the above screenshot I was skipping systems and hiding from time to time as well

I could potentially get it higher if I had a good run.