Everything you need to know about watercolour auxiliaries
Liquid Masking Film is a masking fluid based on natural latex (rubber). The masking fluid serves to protect certain areas of the painting during painting. It can be white light effects or other colours, which should not be changed again. Read more about using masking fluid: Watercolour techniques - use of Liquid Masking Film
For good results, it is important to use a properly glued watercolour paper. Watercolour paper is passed through a glue bath during production to limit the absorption of moisture and colour. With unglued paper or paper with poor gluing, the masking liquid will adhere too much to the paper and the paper may be damaged if the liquid is removed.
Clean the brushes immediately under running cold water. Do not rub because pressure causes the rubber particles to stick together. Instead of a brush, use a cotton swab for applying.