Well not sure I explained it well enough. The thing is that if you just picked blueberry and 1 strain and crossed it and made 1000 seeds. You could plant every seed and possibly not have 2 plants that are the same and any of these fantastic plants that come out of it are going to be a clone only thing unless you spend the time to stabalize the things your looking for and thats not nessesarly easy.
I suppose that if your just looking to throw the dice and see what grows then crossing it with many other strains would work. The only thing is that if you plant that seed and get a fantastic plant you will want to keep a mother of it so that you can clone the thing, because planting more of that same seed does by no means garantee you will get that same fantastic phenotype you got with the 1st one.
Keeping a clone mom and dad alive during the entire process for back crossing is a must if your looking to stabalize certian aspects of a crossed plant strain. If your going to do multiple crosses and save the best of each cross as a "clone only strain" that would be an option. However if your like how this strain grows and how another one tastes to get there offspring to possess both of these qualitys is not an easy thing and will require multiple back crosses to get the desired results and there is still a chance you dont even get those results at all.
edited to add this link:
https://www.rollitup.org/general-marijuana-growing/173816-breeding-seeds.html
Agreed. Grow out at least 20 females,20 males from each strain, pick 3 females and 1 male so you have 3 different desireable phenos pollinated to choose from later , pollenate all three females with one male, collect seeds from 3 females(separated of coarse), grow out 20 from each, choose 1 male from each, take clones of the most desirable female from the three(you could take more, label them them grow the plants out, smoke, choose wich clones to keep from the smoke) Use those clones as mothers, harvest the male pollen sacks from the one male you selected from each group, brush, or shake the pollen from the sacks onto the mature clones that you took. now you can collect those seeds, grow them out pick males and backcross them with clones from each of your mother plants as many times as you wanted. Now you should have three stable varieties of each strain, pick one from each, if you cant, pick 2 and keep 2 or you could cross each type, grow these seeds out from each, pick best male from one strain, and best female from the other strain,pollenate. If you want more qualities from one of the strains just pick your best male from your new strain and back cross it with a clone from your mother plants(which ever one you want). Follow this exactly and you should have a very good strain. Thinking about this makes me realize why seed companies charge so much for there seeds, I mean imagine keeping track of 5 plus strains like this. lol.
By the way sorry about all the improper english and the huge run on sentences, but that was just to much to put in proper form especially when your blowed.....