You may find that the pollen from late stage male clusters appearing. Isn't actually viable pollen. Sometimes that's what you get. Or you may actually get some pollen that way, that will work.
You will also have to expect, to put some time in the project, and devote some space to finding your pollen. And growing out the seeds to see if they are what you want, after you make them. I mean it might turn out all to be crap after you do it. And you may have wasted your time, or you might get something special for your trouble.
A lot of people will complain that seeds are expensive etc. And that you get a lot of seeds from a plant. But that's mostly because they've never made seed, and or then tried to market the product for sale.
For example, my latest crop, will consist of about 8 back cross females, a few will be seeded out. And the rest of what I have going, is questionable if it will be much good.
As the rest of the females I'm flowering are 3/4 ditch crosses. When you get more then half ditch, by back crossing into the ditch weed. A surprising thing happens, not only does the quality go down. But the yield turns almost into nothing. Or at least that's what happened with my last flowering round. As I took, my worst outdoor plant, that had gotten a little ditch pollen on it. And I grew those seeds out and tested them. Pretty much a complete loss for any type of smokeable bud. The plants were almost mutant in nature. Setting up to grow huge buds like it's mother. But, producing almost nothing, in the way of any type of yield.