I buy a huge bottle of ID Glide and decant it into a smaller bottle, it's good and fairly long lasting! I much prefer it to durex, which I find too thick and sticky.
Pre-lubing is a good idea I think, especially when it comes to prodding dry fingers which is all too common. I remember one guy who just wouldn't listen when I told him to go softer on my clit so I went and put some lube on his fingers and he was so confused, he said 'what's this? it's all wet, can I have a tissue'. lol