Switch to Layer 1 and start to do your final lineart. ^^

I use solid black, 1px to do the lineart. You can switch to the Layer 0 to erase the guidelines as you go to get a better idea of how your lineart looks. Just be sure to switch back to Layer 1 when you do the final lineart!! It's irritating when you find out that you drew on the wrong layer... V_V