In the Main window, use the icon to automatically re-circulate previously processed sounds. Try and get a handle on how all the function generators work. Small changes can bring radical differences in the effect. The faster your machine, the more you can do in real-time. You will loose a bit of quality but you can select a smaller value when writing to disk.
Quality is often just as good with small overlaps settings.
Reduce the sampling rate. Write the file to disk. Often, this is quite satisfactory, specially on shorter sounds. Try different values in the DAC and Disk Buffer under the Csound menu to fine tune real-time performance.