Since they are all the same species, then they would very likely cross pollinate and you would end up with a mix of progeny. Most of this progeny would likely favor one type of flower pattern, that may or may not be like either of the parents. In future generations, you would get a more and more homogeneous mix of only one type. So in a case where your originals are all the same species with varying colors, to preserve the color variations you would need to hand pollinate and also prevent unwanted cross pollination that would happen with insects.
Use organza bags (or similar). Something that breaths, allows light in, but not insects. Enclose individual flowers, or flowers on the same stem, before the yellow shows on the center "button" of the flower. petals are inconsequential, and I remove them to make things easier to work with. When the yellow shows, remove the bag and take a soft artist paint brush (not for painting walls) and dab all over the yellow parts. The brush will pick up the yellow pollen and spread it to the ovary receptors. New pollen and new receptors continue to appear, so if you want a seed pod full of seeds, do this every few days until no yellow is there anymore. Always replace the organza bag after each hand pollination. When the yellow is gone, you can remove the bag and allow the normal seed ripening process to continue. But first make sure the pollinated pods are marked somehow so you know which is which.
Remember to dab the flowers gently, don't ever brush or swipe them. This can damage the flower parts and reduce success. Some people use Q-tips, which can work, but not as well. Also, do not use the same brush for different pollinations. There will be pollen left in the brush from the first pollination, even if you can't see it. Your whole purpose is NOT to cross pollinate where you don't want! Dipping the brush in isopropyl alcohol (rubbing alcohol) will kill the pollen between pollinations, but it has to completely dry before re-using. Otherwise, you will also be killing the pollen that you want for the second pollination. Since you will be going back the the same flowers multiple times doing the same pollinations, you could use one brush each for each of the types of flowers you self-pollinate. As long as you don't mix them up, there would be no need for disinfection.
