Engraving and cutting small labels on my 3020 - white lettering on black plastic (1.5mm laser engraving laminate as supplied by HPC) created lots of smoke damage around each label which is a pain to clean off. Also white lettering not white. Engraving with the plastic protection film on failed as well - the letters were contaminated with bits of melted plastic from the protective layer.
Tried LaserMASK from HPC. This is a light blue rubbery 'gunge' in a small tub designed to prevent smoke damage. Initially I thought it needed to go onto the laser laminate as a think film which would then pull off as a thin rubber layer. Not good as the engraved lettering didn't engrave through the LaserMASK!
Then realised that it washes off and that only a very thin layer is needed. Applied very thin layer smoothed out with piece of cardboard (piece of cereal packet about 60cm wide). Hardly used any (which is a good thing considering price of LaserMASK). Works a treat. Can be recommended for plastic etc., but might not wash off without problems on wood and other absorbent materials.
I also found that the smoke from cutting labels out blackened the white lettering near the edges of the labels (no LaserMASK left on lettering). Solved by cutting first (with tiny tabs holding the sheet together) then engraving lettering. Wash off LaserMASK as an A4 sheet then break labels into separate labels and lightly sand the edges to smooth off tabs.
I estimate one bottle of LaserMASK is sufficient for 100 to 200 A4 sheets.
LS3020 used for hobby - making model railway buildings/signals etc.