You cannot determine what dimensions your seeds will have.
As for feminizing, I've understood that there's a chemical that's very popular, that, when applied, transforms all male seeds into feminized ones. This method has a 99.9% success rate.
The technique you are talking about will not guarantee female seeds. I believe that the success rate is around 80%. To avoid pollinating all your buds, pluck the pollen sacks from the plant a week before they'd normally open. Gently collect all the pollen contained, far away from your female and pollinate a single branch or two, depending on how many seeds you want.
As for feminizing, I've understood that there's a chemical that's very popular, that, when applied, transforms all male seeds into feminized ones. This method has a 99.9% success rate.
The technique you are talking about will not guarantee female seeds. I believe that the success rate is around 80%. To avoid pollinating all your buds, pluck the pollen sacks from the plant a week before they'd normally open. Gently collect all the pollen contained, far away from your female and pollinate a single branch or two, depending on how many seeds you want.