I learned to play, playing along to Maiden.
He is such an innovator and IMHO one of the best bass players in the world.
Scott Ian from Anthrax said in an interview. "Heavy Metal is Steve Harris' right hand!"
I managed to catch British Lion (SH's 'other' band) in Birmingham last year and was at the barrier, I just watched his technique all night. Mindbogglingly fast with two fingers I simply couldn't keep up!
I use three fingers for my own take on the style and it works well for the music we play, and I throw in a gallop when I can.
Somewhere In Time is a good album to jam to, there is a lot of bass synth on that too. But, the Powerslave album is the one to master for me.
Listen closely to the title track, in the chorus there's a triplet but, it's a pull up over three strings, it sounds amazing.
I can't get that Phantom of the Opera part either!
Check out hyottoko1 on YouTube - this Japanese guy is a master of the 'Arry style.