I thought it would be hard to firbe glass the inside as well seeing as i'm currently working on my first helmet, but it wasn't that hard.
Only thing i had to do was remove the visor first, after resinning the outside twice, so i could see what i was doing
Oh and make sure u wear gloves that protect you from resin... very messy after 20 mins of work... the stray firbes stuck my fingers together
I've never done the Pepakura thing. It's probably a lot less work on the back end to fiberglass the inside. It's not that it wrong to do it on the outside but you are creating a huge amount more work for yourself. On the inside, it doesn't necessarily matter that it is perfect but on the outside, every flaw shows.