Plane retopology modelling in zbrush
If I want to make a quick simple object I often use this technique. It gets the same results as doing a mesh extract but with more managable topology.
GDI lighting: Global diffuse illumination in zbrush
An alternative to using matcaps, with GDI lighting you light the whole scene with colours you create with a sphere image, great for rim lights and moody scenes. All you need to do is prepare a sphere image and do all your coulored lighting in photoshop. Leave one side dark as you'll use only one light to light the scene. You may also use GSI (Global speclar illumination) and load an image to use specular light shapes like stars and sparkles.
Leaves in zbrush 2.5D
Here is how to do leaves and other similar random particle shapes in 2.5D. In zbrush 2.5D you can DRAW with ztools that will align to the surface of underlying geometry.
Making a quick raygun
Here is the process of making a gun. I drew the gun parts topology on a plane then repositioned the parts and creased edges. I then divided the mesh and used projection master to add detail.
1. fill screen ctrl-f with flat colour medium gray and select single layer brush.
2. choose the line brush option and with Rgb set to 100, draw lines in black
and white. Avoid drawing lines on the top and bottom of the screen.
Switch to the simple brush and press texture- Grab Doc.
3. choose primative sphere 3d and make polymesh3d. Divide to lvl 5 go to the texture and make alpha.
4. In masking choose mask by alpha. The alpha is spherically mapped around the sphere.
5. go to deformation and increase the size slider.
6. if you delete the lower subdivision levels you can mirror and weld to get symetry on your shape.
7. here I have turned the texture on and turned on transparent. Set display to double to see the backface.
8. with a few deformations you can make lots of sci fi shapes. Another tip is to flip the alpha vertically and repeat the masking/size proccess to add more detail.
Try the greeble effect on other shapes and try it with other alphas.