I remember my first was a slow job too. It didn't help that I kept putting the occasional led in backwards. I learnt that before glueing up I should give the LEDs a quick 12v test to make sure.
I can do one roughly now in around an hour and a bit, and that's with my unsteady hands. Tidy takes a bit longer though.
It gets easier mate
Still need to do my spectres. Should get round to it but I keep messing with the PWM converter trying to improve it yet further.