Cutting off the masking tape from clear parts can be done more easier by holding it up against a light, as the lines can be seen more easily. I'd recommend using a desk lamp and not the ceiling light, as the latter will strain your neck. I use a fresh scalpel instead of an X-acto knife, not because it's better, but rather because it's more easily available to me.
As for the masking tape, I use Tamiya Masking tape. It's great because it really seals the area in well which prevents paint from seeping in and allows for crisp sharp lines. It's stickiness is just right that it doesn't remove the paint when you pull if off.
One thing I learned however, is to seal the tape after use to prevent dust from accumulating on it's sides. The dust will reduce the stickiness of the tape on it's side. One work around for this is to trim a little bit off the sides of the tape.
I went the extra mile by storing my tape in an air tight container and placing some desiccant in with it to prevent the moisture in the air from affecting the stickiness of the tape. The desiccant I got were from recently consumed vitamin bottles.
