I will begin by sharing one method of storing pollen.

This very easy method of storing pollen... grab a q-tip. Ruffle it up with your fingers so as to loosen the cotton fibers. Then drag this q-tip through the anthers of the flower you wish to collect the pollen of. Store that pollen in a freezer for maximum longevity. Label your pollen!

Flower ready to be emasculated. One typically wants to remove petals and anthers before they ripen. I remove them with the help of a razor blade. The reason for doing this is that a cacti that is capable of self-pollinating will likely do so if you have not gotten to her early before she has opened and her pollen has matured.

Second, if you allow pollen to mature and her flower to open naturally, an insect may cross pollinate your plants for you. Now, you have no idea who the real dad is...

Easy fix, slice open those flowers and pollinate them early with your frozen or fresh collected pollen.

Now... on another note... a commonly seen problem crested grafts in particular, but it can affect all grafts is the graft lifting up in the middle. What do you do with a poorly graded specimen such as this that has taken, but just barely so it is just hanging on?

My personal take with something this small is to realize that the grafted scion while getting some nutrients from the stock cacti... is also living off of its own reserves at this point. It may even be too small and too nutrient deprived to safely try to graft again.

My method of dealing with a graft that has just barely taken is to bury the grafted cacti sideways so as to allow the scion to root into the medium while the scion also gets a little push from the stock still. It goes a little like this.