Back in 1992 a friend of mine briefly owned a bonsai shop (defunct by 1995). One day I was there and she asked me to help. Serissa in 4 inch black plastic pots, she had 100 of them. I ''picked a front'' wired the 2 or 3 branches, repotted to low grade generic bonsai pots, watered and set into her recovery grow light system. I did maybe 35 of the 100, while she did the rest. We were talking about bonsai, the whole time. Then a month or so later, florist's azalea, same routine, take out of the plastic pot. Put on a few pieces of wire, make 'em as attractive as possible, set them into the recovery area. Did many menial chores for her in between. I learned lots of fragments of the "Bonsai Body of Knowledge". But the repetition of certain activities, like wiring, really helped me.
Nothing beats repetition, repeatedly solving the same problems like pick a front, wire to general shape, pick a ''good enough'' pot from the assortment of production grade pottery. Do this shaping without removing significant branches, let the customer have choices available. I leaned a lot, and greatly improved my own confidence at getting started with material in front of me.
Did a couple years of helping out make me a pro? Hell no. But it did teach me a few things.
So as Walter Pall suggested with the learning Piano example - practice practice practice. And as far as staying in tune? There is such a thing as ''close enough for folk" (folk music).
Some people have "the knack" and very little practice and they are turning out really nice trees. Most of us have to learn larger amounts. "The Bonsai Body of Knowledge" is wide and deep. It takes a lifetime to learn. Nobody ever gets it all. There are distinct aspects, the horticulture for each species you encounter. The artistic elements. The training techniques you would only use on young trees. The training techniques you would only use on older trees, trees advanced toward being show pieces. It is wide and deep. Those that go into bonsai with a solid horticultural background tend to advance quickly. Those that come from creative fields like architecture, graphic artists, designers, they tend to be able to be creative early in their bonsai careers. Dentists tend to make particularly well detailed bonsai. The smallest detail the dentist is willing to work until it just perfect.
So we all come to the hobby with different strengths. My strength is I know basics of horticulture. My weakness is artistic design. I use formulas because quite honestly, I often do not have the artistic vision to ''create'' out of the blue.
So it is not a simple question.
@AlainK - That cartoon is exactly like the way grandparents and their generation would speak, though I believe the dialect of German the cartoon used was Yiddish. My grandparents spoke Schwabisch, Sie sind Donauschwaben. For those that don't know, an area along the Danube River at the eastern edge of modern day Hungary, where it borders Serbia and Croatia. My great-grandparents emigrated to USA just before WW1, bringing my grandparents who were already teenagers, so they were already ''fixed'' in their languages, and always had noticeable accents. They settled in Chicago, in a neighbor with many Donauschwaben, I remember walking to the grocery store with my grandmother, and the old folks (her age at the time, younger than me now) would be sitting on their front porches. The conversation was in exactly this sort of mashed up Schwäbisch-English-Hochdeutsch with some Hungarian or Serbian too. Point, I get the cartoon.
But then again, I am being too literal? "I'm beginning to think you are right"