Sieves are an essential for a good glaze finish, try and get an 80 mesh as a minimum.
When trying out a new glaze 2kg of powder would be sufficient to enable dipping of mugs or other small items. As a starting point 1kg of water should be added per 1kg of powder. When working with any powdered glaze materials you should definitely wear a respirator mask. A fine sieve should be used to pass the mixed glaze and remove any large particles. Sieves are an essential for a good glaze finish, try and get an 80 mesh as a minimum. They are available from pottery supply places.