Methyl Cellulose is sold in powder form. The best powder to use is pure methyl cellulose powder of edible quality. It costs only a little more than that of industrial quality. It is used in cooking for thickening sauces and ice creams.
MC paste is water soluble and will rinse out of clothing, especially when still wet. It does not usually leave a stain. We do not suggest eating or licking it ~ although it does not contain any harmful ingredients. Wallpaper paste is similar. It is reformulated into flakes, to aid dissolving and dispersion ~ and it also contains extra chemicals ~ to reduce lumpiness and help mixing and spreading ~ and fungicides ~ to kill bugs. We do not recommend that for unsupervised use. Try to avoid breathing any dust when handling powders of any sort.
Methyl Cellulose powder is slow to dissolve, and so it is best to make paste some hours ~ or the day before ~ before it is required for use. Chemically it dissolves in cold water, but not hot. Physically it mixes with hot water but not cold. This is difficult to understand, and goes against experience. Ideally ~ take the required amount of MC powder and mix it with about twice as much quite hot water ~ over 70ºC ~ to make a smooth paste. This can then be mixed with cold water to the required total volume. It is best to leave it overnight for any invisible lumps to dissolve. Storage in the fridge is often advised ~ but is not necessary if you are using it frequently.
Put about one heaped tablespoon of paste into into a 'half-kilo' glass jar. Have a spoon or stick ready for stirring ~ then add about a cupful of water ~ hot if possible. Stir vigorously, especially at first, to make a paste and try to avoid lumps. Add cold water ~ continue with the stirring ~ to make a five or ten percent mixture. The paste is ready to use when it goes clear, although that may take some hours. The paste will keep for several weeks without the need to refrigerate.
If experimenting then I would suggest you have another glass jar or two ready. If the mixture is too thick ~ and maybe lumpy ~ put half into another jar. Jars with good screw-top lids are useful ~ they can be vigorously shaken ~ especially if they are not overfull.