Use mixer cups. Volumes are marked on the side. So, for a 10/1 ratio for example, measure out 1 litre of lacquer in one cup and pour in 100 ml of catalyst into another, mix, stir and use. Also, measuring cups have guides on the side for various proportions, e.g., 3/1, 4/1, etc, so if you only need a small amount of lacquer, i.e., no more than the volume of a single measuring cup you may be able to use these marks. If you do an online search for 'paint finish mixer cup' you'll find several videos and cup sources. Slainte.