Personally speaking, I would recommend the vertical method for addition and subtraction which is most probably an easy one and it won't take up that much time in solving. As what I have stated, it doesn't imply that I won't be helping you with this, but was just an expression of my perspective. Anyway, as for subtraction, the easiest way to do it with a number line would be a reverse number line. This means that the numbers from the left to the right are decreasing.
Which looks like this:
<--36--35--34--33--32--31--30--29--28--27--26--25--24--23--22--21-->
Now we'll have the subtrahend, which is 17, to be broken apart.
17 would be broken into 10, 5, 1, and 1
Then to the number line:
So we move from 36 to the right for 10 numbers
<--36--35--34--33--32--31--30--29--28--27--26--25-->
which ends up at 26. Then from here, move again 5 steps
<--26--25--24--23--22--21--20-->
which end up at 21. Then from here, move again 1 step and another step. or simply move 2 steps from there.
<--21--20--19--18-->
which ends up at 19.
So the 19 would be the difference of 36 and 17.
NOTE
When presenting this, it would be advised to make one continuous number line to accommodate all the jumps and mark all the movements and label them jumps.