My favorite is finding those people within your guild/friend list, that self level, and believe me, there are lots of those people, that operate outside the FP swap threads. In those situations, you can get some nice rewards, with fairly inexpensive contributions some times. And because they operate outside the Swap threads, you can kind of sneak in there quietly, make your contributions, gain your rewards.
I've aggressively placed FPs on a guildies GB, to ensure I acquire blueprints, medal, FP rewards, when it was a GB I was trying to accumulate blueprints for.
I've also made a point of taking top spot at advantageous times.
But I avoid the obvious last minute 'snipe'.
I've never had a guildmate call me out, for the way I've gone about placing FPs, onto other's GBs.