Hey yall

I'm trying to make a mold out my hand, in a finger-gun position, for my sculpting class, to then cast it in plaster. Its to make a model to later sculpt from scratch. I'm using alginate and am on my third failed attempt (i'm the only one who's failed so far). First one i did in class, two hands, like if i was holding the fingergun (recommendation of the teacher to "not wasted too much alginate" because i was using a 5L bottle, i have biiiig hands) failed because too much alginate entered inside my palm and created flappy walls that got in the way of the plaster. Second i couldn't get my hand of the 2L bottle (we are using bottles cut at the top to contain the mix) and totally shattered the alginate on the way out. That thing was farting and tooting. Third i used another 5L, but my problem was that it was too bubbly. The way we mix the alginate is inside the bottle, with a hand blender, tepid water and slowly pouring the alginate powder as we mix until we feel like the consistency has changed to a sort of cream? Im not too clear on that. Do you guys know why i failed the third attempt ? It was my closest one yet but all the bubbles totally ruined the surface of the hand.

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TLDR: how do i prevent bubbles from forming in the alginate ?