If you are working like these examples shown, you are using way too much of resin and this ends up in a weaker and heavier part.
The use of this batting like stuff is cheap, but only good for covers with no load, but a big mess to work with any way.
A good fiber cloth can be draped very good, is multiple stronger and will give a light and firm part.
Here are some instructions (only German, but a lot are with pics, so even if you don't understand well, useful):
suter swiss composite group