Yeah. I imagine people actually do read a few good tutorials at some point when they first start to customise, unless they have some older friends or relatives who will teach the same stuff. However, that's just the beginning. Just like you can read some tutorials when you begin to use a whole new computer program (like 3D modelling). But following tutorials only takes you so far, plus, like fireheart said, it's not really your custom model if it's made following tutorials, not your own imagination. Naturally a custom models isn't everything, either, since you'd actually need to be able to use it in combat with 100% efficiency. I doubt Sekai is even close to that yet with Iori's gunpla.