Sometimes you'll find that you learn French fast when you take emphasis off of the actual language from time to time. This can be done by learning music, where the music itself is part of the goal, or by actually using the language for practical needs. When you need to learn numbers, you may want to think back to how you learned both numbers and the language required to work with them as a child. Simple, direct math problems oftentimes provide a great way to learn language skills that everyone needs for day to day transactions.
French and English are very similar, in many respects. They tend to express the relationships between numbers and mathematical concepts in similar fashions, as well. For instance, you can say "two take away one" and have it understood to mean the mathematical problem 2-1 in French just as you can in English. You can quiz students, or make up quizzes for yourself, that involve math. This will help you learn numbers very quickly. Because you're concentrating on the math problems themselves, you'll be able to see through any problems with language you may have toward your greater goal, which is finding the answer.
This can also make it more fun to learn in French classroom settings. In some language programs, you might learn to count by memorizing numbers and learn some very basic math-related words. You need to actually hear and work with numbers before you'll really understand how to speak this part of language fluently, however. Some materials have audio plays that are used as a form of immersion learning. If you want to use these to teach numbers, look for ones with complex stories that involve characters performing actions such as buying groceries or other goods, filling up cars or other everyday instances where math is required.
Just as is the case in English, you can learn French songs that help with counting, as well. Math is a common theme in folk songs and children's songs, where each verse counts up or down as part of the song's story. Melody is a great way to remember complex information, such as the progression of numbers in a foreign language. Generally, learning to hear and speak French numbers is more important than learning to write them out in word form, which can be taught later on and which will not be used as frequently.