The CMYKGLW ink configurations of these devices allow the use of Varnish and White as Spot Inks. To configure them, you need to:
1- Use one of the CMYKGLW drivers, depending on your printer model.
2- Select the right resolution and quality to achieve the wanted effect.
3- Then go to the Page Setup module:
4- Open the corresponding tab, and then click on Enable separation:
Info
To have more details on the topic, please refer to this article dedicated to Spot Inks.