Ditch ready mixed 'one tub does all tile n grout'. Absolute rubbish! If you want to use ready mixed then do so, but use a proper adhesive and a bagged grout, leaving at least twenty four hours between tiling and grouting. Using this method you will not need to prime plasterboard of any type.
However if you decide to use a bagged adhesive then all plasterboard WILL need priming with SBR or a primer designed for tiling, ie NOT PVA!
Are the tiles ceramic or porcelain? This will make a difference to the adhesive used. Ardex D20 is a readymixed adhesive suitable for either but cant be used on non absorbant substrates, such as painted surfaces etc.
If you keep the readymixed stuff you have you're asking for trouble!
However if you decide to use a bagged adhesive then all plasterboard WILL need priming with SBR or a primer designed for tiling, ie NOT PVA!
Are the tiles ceramic or porcelain? This will make a difference to the adhesive used. Ardex D20 is a readymixed adhesive suitable for either but cant be used on non absorbant substrates, such as painted surfaces etc.
If you keep the readymixed stuff you have you're asking for trouble!