Generally, for the purposes you describe, to make 10% gelatin for sizing:
900 grams of water at room temp (20C)
100 graams of 250 BI gelatin (Bloom Index which has nothing to do with blooming gelatin)
Gently stir the gelatin into the cool water and begin warming to 40 deg C. Hold there until all gelatin has melted and dissolved. Add preservative and chill set until use.
This entire process is called Blooming.
There is an alternative method also called blooming and is used for addition of solid gelatin to an emulsion or any gelatin based alternate process.
Take 100 g of gelatin and add small increments of ice cold water (under 10C). Just wet the gelatin and then allow it to worm to 20 C while absorbing that cold water. Record the weight change. This gelatin should not be stored but rather used immediately.
When needed in your formula, add the required amount of Bloomed gelatin noting weight of gelatin and water to get your total change.
In many cases, this sort of blooming step is omitted and gelatin is added directly to the hot light sensitive mixture.
So, as you see, there are basically 3 methods of getting from here to there and two of them are called blooming gelatin but use entirely different methods and which are often used for different purposes.
I hope this sheds more light on the terminology and your question. Sorry about the confusion.