Locate your umbrellas so that they allow you to dissipate the light to create a softer look. Also, you can use them to reflect a stronger light, thus achieving a brighter appearance, without discoloring the subject.
To achieve softer lighting, use the white umbrella. Once opened, you can illuminate directly through it, which will remove strong light and at the same time provide a dim glow.
Orient the lights. If you want the shadows to disappear, you can use the white umbrella. When reflecting the light through it, place it so that almost all the light is behind the subject. The shadows will disappear and you will get a more delicate outline. This type of shots is preferable in portraits and other locations where shading is common (for example, outdoors).
Use the silver / black umbrella to illuminate the subject. This type of umbrella is black on the outside, but when turned over, its interior is silver. When you direct the lighting to the silver side or the bottom side of the umbrella, it will reflect on your subject. Regulating the lighting in the subject may take several minutes. However, once you are finished, your subject will be brightly lit, without being discolored.
Combine the white (translucent) and black reflective umbrellas in one shot. In this way, you can hide the shadows and give the subject a healthy glow. To achieve a professional image, use the reflective umbrella as your main source of illumination, then use the translucent (white) umbrella and dissipate the light behind the subject.