EDIT: Please also read the comments, especially danzo321 has written really good advices, since I'm not an expert but sharing my experience reading the comments would make your process easier =)
This time I am going to show you how to take an alginate mold of a face (and fill it with plaster)
What you need,
A model ;)
Several cups (to mix, pour water etc)
A pillow (you have to make the model comfortable =)))
Small pieces of paper (or you can use straws, I didn't have any so I used paper)
Have your model put vaseline all over her face and hair and put the cottons in her ear, roll the paper and well stick them into her nose so she can breath =D
Mix your alginate with water
Now if you have people around you make them help you =) It would be much quicker if someone else also mixed alginate with water in another cup so you guys can pour it together. I had only one extra so I made her take the pictures and did all the mixing myself.
If there isn't someone to help, be patient, don't try to mix huge amounts of alginate cause they are going to dry quick and you probably will waste a lot of alginate.
REMEMBER! If alginate is getting light pink it means you only have a few seconds to pour it on the face. Best to use it while it is dark pink/purple.
I needed the ears and the chin for my project. If you need the ears, make sure you blow air to the ears while pouring the alginate, if not it won't get in the ears and you won't obtain an ear mold =)
Make sure to put an extra coat of alginate on the ears and lips.
And wait for a few minutes, not much 2-3 is enough =)
Have your cup of water near you and dip the plaster bandages into water and cover the alginate mold.
Make sure you have big and small pieces of plaster bandages, use the small ones on and under the nose.
I used 2 or 3 packages of plaster bandages. 1 is not enough and each package was 2 meters.
This time wait for 10 to 15 minutes. You have to be sure that the bandages are hard enough to hold the alginate. Cause you are going to pour plaster in it afterwards and if the plaster bandages are thin or are not hard enough all your work will get wasted.
This is the hardest part
Taking out the mold. It would have been a lot easier if I didn't need the ears...
Slowly wiggle the head out of the mold. While the model shakes her head hold the sides of the mold so they won't tear.
Now on to easier steps,
Mix your plaster with water. Pour it into the mold. Don't wait for the plaster to get thick, the first coat should be more liquid-like, so there won't be any bubbles and you would get every little detail =) Mine wasn't and thus I had a huge bubble over the lip, though after I remade it by slowly adding thin coats and coats of plaster, which was just because I poured the plaster while it was a little thick, like whipped cream.
Wait for a day, two is better cause the layer of plaster in there will need a day or two to harden.
than wiggle out the head, use a sandpaper to polish it and voila =)