Primer is normally used to promote adhesion and to give a better finish (can be rubbed down easier and finer than base surface) Also it lessens the chance of reactions.
Although saying that some paint let you get away with it like enamel or acrylic as long as the surface underneath is take to 600grit wet or a red scotch pad then applied in dusty coats untill full coverage is reached.
Generally it will be (for a good exisiting paintjob) scuff frame to 600wet or red scotch, light coats o primer until covered, scuff with 600 wet again to rid any dust nibs, then light coats of top coat until covered then laquer over the top
Primer is normally used to promote adhesion and to give a better finish (can be rubbed down easier and finer than base surface) Also it lessens the chance of reactions.
Although saying that some paint let you get away with it like enamel or acrylic as long as the surface underneath is take to 600grit wet or a red scotch pad then applied in dusty coats untill full coverage is reached.
Generally it will be (for a good exisiting paintjob) scuff frame to 600wet or red scotch, light coats o primer until covered, scuff with 600 wet again to rid any dust nibs, then light coats of top coat until covered then laquer over the top