when the pollen appears, put a piece of newspaper or similar under the plant to gather as it falls. take a paint brush and 'paint' the areas you want to have seeds and it'll cut the saturation a bit. some will still float around, especially with fans running but you can minimize the amount by separating and painting. it only takes a very small amount for a shitload of seeds...
they're ready for pollinating as soon as you have both pollen and flowers.