How do i paint over varnish?

i hve been told cetain paints react to varnish, but how do i paint over it,what do i use?How do i paint over varnish?
seal it first, then paint over itHow do i paint over varnish?
sand down the surface then use a undercoat let it dry and give it another undercoat if its patchy
strip the varnish off first with paint/varnish remover.
Try sanding off the varnish, and then paint it with bullz-eye an alcohol based primer. It seals the stains and adheres to almost anything.
Paint will stick to varnish, but it will chip off easily. Get varnish remover from your DIY shop, but wear a face mask as the fumes affect your voice. If a jobs worth doing, do it well Sand down and treat as new wood.
rub the varnish til shine gone put on undercoat then topcoat.
Paint might crack if coated over varnish, better to take it down to the bare wood, and start as new wood. If you use paint stripper remember to wash the wood thoroughly before painting,

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