With Annona, first day flower is narrowly open - it is a female stage. The next day the same flower opens widely, indicating a male stage. That’s when you collect the pollen in a little container. If no female flowers found at this time, keep this container in refrigerator for up to 48 hrs. Next day look for female flowers and transfer pollen to them with a soft narrow brush. Collect fresh pollen from the male flowers. Flowers on my annonas are usually ready for pollination around 6 PM.
I did try to pollinate Rollinia with Atemoya pollen. Nothing took to far.