What size masking tape should I use?

Masking tape comes in various size widths from 1mm to 18mm.

The size you use would depend on what it is you intend to mask.

It is best to leave painted areas for 24 hours to dry prior to masking, if tape is to cover existing paint.

Some masking tapes are designed specifically for model making, which have less tack (stickiness) and therefore tend not to remove previously painted areas.

You can use household masking tape, but this tends to be far stickier. One way around this is to cut your masking tape to the desired length and then place it on your trousers for example and then peel off, this will make the tape slightly less sticky, and give better results (you stand less chance of damage to your models).