At least this works on pine seedlings. Haven't tried on collected (or bought) ones.
In May: Remove all the candles
In June: Remove all the largest candles
In August: Pinch all the largest candles and pull off old needles
As you may understand, this tecnique works best on small trees because you must pull off all needles that are over a year old to make all needles left smaller.
Anyway, the next year you may leave last year's needles there too as they are also small.
And as the others have also said, your tree's wonderful! You could easily sell your pine bonsai (with a good price) and you're asking if you'd give up on them. Huhhuh.
