Use flashcards. Make multiplication cards for each number set. Although this may seem tedious, the process of making the cards will actually help you to learn them. Once you’ve made them, spend some time each day studying until you know them all. Focus on one number set at a time. When you go through the cards, put the ones you get wrong back into the pile so you see them multiple times.
If you make your own, you can just draw three circles on a page and then 2-5 triangles on a page, and ask the child to match each circle with a triangle by drawing a line from shape to shape. Vary the shapes and the amounts. Sometimes the amounts should be equal, sometimes not.