Get them to say it as: one’s 4 is 4; two 4s are 8; three 4s are 12 and so on. Give them a chart to look at that has the times tables set up this way. They then have to say each line 3 times to themselves. They can use their fingers to help know which one they are up to. Afterwards you test them.
Get them to do this in the evening before going to sleep. The next day, they will have a better chance of remembering.