Proper term i guess is mold making/casting will get you all the vids/info you need.
Theres platnum cure silicone --costs more
Or tin cure silicone but the molds dont last as long as platnum
But certain things need the correct silicone to mold well
If u need a quick list to experiment with try these: go to "smooth on" site
Get tincure moldmax 30 -- for mold rubber material
Get smoothcast 65d urethane -- for plastic finished piece
then FOLLOW the directions!
Your inside finished piece will be hard plastic kinda like a white (unless u add color) soda bottle cap
Pick up plastilene clay from a craft store to help with molding and wont react bad w/silicone
I've been using azek the plastic wood/boards for mold boxes (scraps from work)
Then there is also colors you can add or a uv protectant additive even glow in the dark additives
Then theres the mold release spray too
Many different types of materials are out there but starting with these two products will get u going.
Dont forget gram scale.
Lots of paper towels+plastic cups+stir sticks
If u want to mold a rubber piece well thats different. a clear lense (like tailight) is a different material also and the Tailight would be a translutient(sp) color not solid.
Lots of info out there just dig around for it,
Good luck i hope u try it/ just remember that i'm just a recent beginner also, but learning.
Shep