#1 - Do you want chicks or not?
If you want chicks then get a M/F pair, if you do NOT want chicks get either a M/M or F/F pair.
Give them a choice, and the urge to breed will cause them to form M/F pairs.
I keep my non-breeding birds separated by sex, in separate male and female community cages. They will form buddy pairs and bond.
One thing to watch for in these same sex pairs. The dominant of the 2 will sometimes pluck the other bird, and sometimes pluck it a LOT.

I don't understand it, but I think there is some kind of submissivness where the non-dominant bird will allow itself to be plucked by the dominant bird.
#2 - Do NOT put ANYTHING in the cage that might trigger a breeding behavior; no nests, no nesting material, etc. Limit the amount of egg you feed them, as I think a lot of egg might trigger them into breeding mode also.
And VERY important, keep the males and female out of visual contact with each other. The males can go nuts when the see a hen and want to mate with her.
Distractions would be
- a bath
- swings
- space to fly (long cage)
- food (nothing high in protein, I limit the amount of egg I feed my non-breeding or non-molting birds)
#3 - I would NOT use ANY sprays/scents etc of ANY KIND around or in the same house with the birds. As was mentioned, we don't know what in these things might be toxic to their small lungs that we won't even notice. Miners used to take canarys into the mines, and when the bird died there was toxic gases in the mine. I make my wife use her nail polish remover OUTSIDE the house or in the bath with the exhaust fan running. A central heating/air conditioning system will move any toxic gas all over the house, so being in a part of the house is not adequate.
Better safe than sorry. And the more $ you have invested in your birds, the less you want to take a chance.