The former Real Madrid forward opened the scoring after 14 minutes to settle any nerves at the Arena AufSchalke, and rounded things off with nine minutes to go after Klaas Jan Huntelaar had made it 2-0 in the 54th minute.
It was Felix Magath's side's second league win of the season, with their other success coming at Freiburg on September 22, and it moved them out of the relegation zone.
It did not take long for Schalke to find the rhythm that has eluded them for so much of the season, when Raul got in at the back post to get on the end of Astuto Uchida's cross and open the scoring.
St Pauli should have equalised before the break, though, with Deniz Naki failing to make the most of a free header from six yards before the same player scuffed wide when clean through on goal.
Naki was made to pay for his profligacy early in the second half as Holland striker Huntelaar put Schalke further ahead.
Huntelaar, who played with Raul for Madrid, found space from a Jefferson Farfan corner to get a header on target that evaded Thomas Kessler in the St Pauli goal.
If the result was still in any doubt, Raul finished things off in the 81st minute when he made the most of some indecision in the visiting defence to tap home from close range.