Preseed question

Okay since AF showed up today I am back to CD1 and hoping this will be it!!! I'm going to be drinking a lot more water and trying preseed this month. I was looking on amazon and there are different types of it. Which is best? Also, I saw you can insert it vaginally, is that the best way to do it? And if so, how long can you insert it and it be good? Because I'd hate to pause the Foreplay to insert it. TIA.