my DS is also 6 months old but he has no idea of any routine. i am lucky that he will happily go about his day as long as he is occupied. a big day running errands and such, may be out and about for 5 6 hours and he wont eat the whole time. i will make time while i am out btu he is too distracted.

i will admit i have tried the FPS but it really depends on his mood. he will on occasion try all at once. feeding is a game sometimes which involves spitting milk at me, then bang he is asleep. then i will go to put him down and the play begins all over again.
i think it is most important to do whatever works for you. and try to read their cues more than anything.

there are no such things as rules!