Tracing handwriting on after effects

Hi,

I am tracing handwriting on after effects using the pen and stroke tools, i have traced all of my letters perfectly but the letter s keeps on picking up another bit of the s(see image) and i cannot seem to fix this. The only thing that makes it go is when the brush size is very small but i want a high brush size but it just wont trace round atll. Any tips please?? I have tried creating two separate masks but it just doesnt work at all for me