To apply any plaster finish you will need a trowel. Most importantly make sure it is made of stainless steel and sharpened at all edges. All trowels come with a small bevel but need to be sharpened especially if your applying a high polished finish.
Do NOT use a drywall taping knife. Getting proper hand troweled designs are much more difficult to achieve. The trowel is made especially for these materials and you can use a specialty trowel for other circumstances or designs.
You will need a Hawk to hold your product and carry it with you. Also you will need a few different size putty knives, These are your main tools you will need for any project.