I fixed pretty much all of my problems:
1. I moved the car out of the garage so that I can work in there (I also brought in a table and a chair). Now I have loads of free space.
2. I fixed the bumpy parts of the helmet using something familiar- sandpaper. Except that the sand paper I was using was shaped like a sponge, but it still worked perfectly.
Right when I was getting happy about all this, another problem jumped out of nowhere. The helmet seemed to be a bit too small. I kept on carving the inside to make more room, but I ended up with a crack near the front top part- which I can fix very easily, but I don't think I will. Why? Because it's so easy to make armour out of foam that I can just start a new, bigger one.
Maybe I'll think of fixing this one, but I don't think it'll be big enough.
PS: And If I have any other problems, I'll be sure to ask you blackrose.