Where all has Warfield written on apologetics? I used to have the ten volume works and his selected shorter writings (I think). All I have now is his introduction to Kuyper.
Part 1 of Selected Shorter Writings vol. 1 is almost exclusively focused on apologetics. Writings of Part 1 include: "Agnosticism", "Atheism", "How to get rid of Christianity" and a few others. I can send you any other information you want on them.