Adding Dirt!
There are several options for adding more grit. Firstly, the wave type you choose will naturally sound smoother or more gritty (for example a smooth triangle vs an angular square). The level of these waves in the mixer will add more/less saturation too, depending on how high/low they are set. In turn, the level coming out of the mixer into the filter affects how hard the filter is driven by the oscillators and thus can subtly or noticeably change the way the filter (and particularly the way the resonance) reacts/behaves. Often very subtle level changes/blends can yield great results. Finally, don’t forget the analogue distortion.