Meths + gentle rubbing with a toothbrush, then into a washing machine for a Synthetics or Delicates wash.
Or the above but vodka instead of meths.
Apply a tiny amount, use a toothbrush, gently brush and loosen the top layer, then more of a scrub afterwards if paint is removed. Maybe test in a less obvious area first.
If the fabric isn't delicate and 'for best', try something like Flash all purpose cleaner, the kind of thing that boasts of cutting through grease and grime, (maybe not the pine scented variety!) or Mr Muscle oven cleaner. Again, apply a small amount, work it with a toothbrush before putting it in the wash.