Hi
A long time ago I devised a colour-coded system whereby you group the tables together in 'families', each 'family' having its own colour. So instead of (trying) learning them in the conventional order - 2, 3, 4, 5, 6, etc - learn them a 'family' at a time. Type them out in a bold font, and print them off. You will then see the relationship between the two or three tables in each family.
Thus, the first and easiest family, which you have implied DS already knows, is: 5 and 10.
The next easiest group builds on 2 and even numbers:
2 and 4 and 8 are a family, and the relationship between them should be obvious.
The last 'family' is:
3 and 6 and 12 and again you should see a relationship.
That leaves the odds-and-sods:
7 and 9 and 11.
(and if you can understand all that you are pretty clever!)
Pity we can't tab and colour on here, but hope it helps a bit.
cheers