Sprinkle the baby powder over the oil spot so the whole area is covered. Leave it for five minutes then brush it off with a soft brush to get rid of oily baby powder. Some of the stain will probably still be there at this point.
Cover the oil again with baby powder. If the oil has soaked all the way through the fabric and you can reach the other side, apply powder to that side too, using your fingertips to gently rub it in.
Leave the baby powder on the polyester overnight. In the morning, use a rubber-tipped spatula to remove most of the powder.
Brush the area softly with a soft brush to remove powder residuals. Look at the spot. If it still looks like it has some oil, reapply fresh baby powder and leave it on through the day.