Ok I play skyrim on ps3 and have finished the Dawnguard questline as a Vampire Lord. I have Serana as a follower. How EXACTLY do I use a Potion of Blood to be a Werewolf and Vampire Lord? And if I'm both will I still have all the same abilities as a Vampire Lord or will certain abilities dissapear? Help please this is very important to me!!!
You will retain all your abilities in either form, but your human form will either be vampire or mortal depending on what you last used.
For example, if you use Vampire Lord and revert, you will be a vampire (orange eyes). If you use Beast Form, you will become mortal (normal eyes).
I'm assuming you joined the Volkihar Clan from your post. After you use Beast Form, just remember to use Vampire Lord form if you want to talk the Volkihar Clan.
However in truth you have no need for Potions of Blood as you will be stuck in Stage One. You can only Vampire's Sight or Vampire Lord for your Vampiric Powers due to this. I honestly haven't been bothered by this, but you may be.
Another thing to note is that the Ring of Hircine and the Rings from the Frostmoon Pack will still work in Beast Form.
Hope this helped. This is from personal experience.