Yes A long term thing , but time does pass so why not grow out the seed of you experiments,.
I was reading something yesterday , but really do not think you should over complicate it with some scientific stuff.
It does not have to be that complicated though
After you get your seedlings you can graft those onto a large tree to speed up the process
(Like Okrain said certain plants can make clones of the Mother tree, even if they where pollinated )
People also Back cross (like Inbreeding)
That is A (mango ) crossed with b mango =c
Breed the offspring C mango with Mango A (or B)
Also Most the people that talk about breeding here talk about citrus here
(maybe mango, but I do not follow mango here much or lately
Coconut He hybridized Latex less Jack fruit Very Funny Posts,,
but not sure you could learn off them No offence , but I do not think He explained his Technique ..)
You may be able to even make a hybrid of a Mango, with the one of many different mango species.
This is pretty easy to read (explains sterile Mule of a Horse, and donkey.)
https://www2.palomar.edu/users/warmstrong/hybrids1.htm