Try a speed test number grid.
Get squared paper or make little boxes.Easy to knock up with a ruler and pen. Start with a small box, perhaps 6 by 6 and use his most well know tables. Mix them up from left to right at the top of the grid horizontally. So it might look like this; 3,5,2,10,6,11
Do the same again for vertical numbers but choose different numbers e.g. ,5,7,9,10,12,8
Give him a stop watch. Complete the grid. He can go in any order lt to rt. mixed, top to bottom. It doesn't matter.
Write his time down. The first time will be slow getting use to reading the grid.. Get him to beat his time and reduce errors. Playing against himself. Increase the grid to 7 by 7 etc all the way up to 12 by 12.
Lots of variations of this game. Depending on your views on rewards they work well at the beginning to get them to persevere reading the boxes, which is sometimes a new concept. But not something that should be relied on. I found recording the time and trying to beat it was reward enough. I joined in myself to sharpen my skills. I got them to circle the wrong answers and it was for them to find the right answer. or I'd tell them if it was too much. Keep all the grids in one book. It's good to look back on and see how far they've come. Fun activity to do before dinner, on a car journey. Get siblings, family to give him 8 numbers between 1 and 12 in any order( e.g.for an 8x8 grid) or set up a bowl of numbers and he chooses in random order his numbers. If he struggles- keep the numbers in order 2,3,4,5,6 then 3,5,6,7 etc then start mixing up 2,5,4,6,7,8 etc go at their pace.
Hope that helps
I loved this game with 10-11 year olds at school they loved it.
The game is supposed to be fun. It'll identify if there are problem tables eg. 8x8 8x7