DP is awesome! Making sure she's good and lubricated is best. I always tell my husband that if he wants anal, then that's the last place he plays in because if you go back and forth from hole to hole, you risk UTIs and that's no fun. So, if you DP your GF, make sure that you play in the front first, insert a toy of choice, and then play in the rear

Depends, if you want to be vaginal I suggest Doggystyle and then put the dildo in anally and have it rest on your pubic area as you thrust so will the dildo, if you want to be in anally have her lay on her back and same concept put the dildo in vaginally leave it rest against your pubic area and as you thrust so with a dildo. Ps works better with Suction cup dildos, Hope this helps