Global Colours Gesso Medium is recommended for surface preparation and sealing.  It is flexible, fast drying and permanent.
Gesso Medium is best applied with a broad brush or cardboard wedge, onto a surface free from dust and grease.  Dilute with 25% water to allow for absorption into surfaces of varying porosity (e.g. concrete, wood, canvas, plaster, etc.). 
To achieve a smooth surface apply several thin coats with a light sanding between each coat.  To prepare for oil painting, apply a minimum of 3 coats of Gesso.  Allow 1-2 hours between coats, depending on the weather conditions and temperature.
This medium is compatible with the range of Global Colours acrylics and other mediums, working together to create a highly versatile painting system for all artists.