I homeschooled my daughter this past year, and Saxon Math teaches many of the multiplication facts by counting in multiples (3,6,9,12,15,18,21,24,27,30,33,36,39, etc.) of that number.
I don't know if your child has problems with any of these--my daughter has just finished second grade and is really in the early stages of multiplication, so it helped us to count in multiples every day. It's something that doesn't require a lot of concentration or flash cards and can be done while you're in the car, waiting for something, or just have a few down moments.
Another thing--I always urge my daughter to use what she knows to figure out what she doesn't know rather than relying on rote memorization. It's easy to say "I give up" on a difficult math fact such as 7x9=63...but if you encourage your child to use an easier math fact such as 7x10=70 and then subtract 7, it breaks down the "I don't knows" to "give me a minute to figure it out"...