I would never use Vaseline, which is a petroleum product. Bad glide. My fave is silicon lube, and the Germans make an awesome one called Eros. Not cheap, but it doesn't have to be reapplied as lesser lubes do. Can use used with latex and poly condoms, whereas Vaseline (or anything oil-based) will break down a latex condom FAST.
If one maintains a healthy diet with regular BMs, an enema is not necessary. Enemas too frequently are bad for the GI tract, flushing out beneficial bacteria from the gut and such. If you have a good diet with plenty of fiber, there will not be any fecal matter "left over" inside the anus.
Sex educator Tristan Taormino wrote an excellent book called "The Ultimate Guide to Anal Sex for Women". She demystifies everything about it in straight-talking terms. I would highly recommend this for anyone who engages in anal play. She also has some videos on the subject as well. Hot dirty fun done right