The air cooling usually requires about 40 psi which will result in a flow rate of about 1 SCFM.
Higher pressures can be used for higher flow rates, but the noise level increases along with it. It does not need any special filtering.
Liquid cooling is generally used to thermally isolate the structure to prevent thermal expansion, not make a motor work where it otherwise would not. The cooling will depend on the fluid being used as well as other factors. The general specs are as follows:
0.5 to 0.7 GPM flow rate
Approx. 20% increase in Watts removed
Approx. 10% increase in force capability
The WinTips sizing software has both AC and LC options as selections.