Working with Alphas:
If you want to apply an alpha (I usually choose Standard Brush - may also duplicate the brush), choose DragRect, choose the alpha and apply (left mouse click and drag til the desired position). Playing with Zadd, Zsub, Z Intensity value you may tweak the result.
Alphas are black to white images, you may prepare your alpha in Photshop, save as .bmp .psd .jpg .gif .png .tiff .tga (the supported formats), in Zbrush - click Alpha - Import. (I think one donwside of Zbrush is when you re-work your alpha, you have to import it again and that does not overwrite your previous version, just adds the newly imported alpha - i think its a pain, ending up with several "same" looking alphas" in the thumbnail preview window).
To be able to move an alpha when applying to model surface
hit "G" (for Projection Master) - choose Deformation and Normalized (checked only) - the Color and Material are NOT checked, Drop Now. Apply your alpha, when moving it choose move, rotate tools, when you are done hit "G" again and choose "PickupNow".
On a brush choose an alpha, go to menu Alpha - press "Make St" - a transparent square appears. To be able to activate and work with it hold SPACEBAR (Zbrush 4 or right click Zbrush 3). You can move, scale and rotate the alpha. Then choose Alpha Off and with a desired brush draw over the sqaure to get the result. Go to Stencil Menu and turn the Stencil off.
CREATING ALPHAS in Zbrush
Choose Document Menu - size 256x256 and Resize.
Get Plane3D, draw on canvas and choose Make PolyMesh3D (in tools menu button). Then choose that tool and Edit. Divide a couple of times the rectange (Geometry - Divide - make sure you turn OFF Smooth (smt) ).
Draw some shapes with the brushes and when you are done, go to Alpha menu - GrabDoc.
To make alpha tilable.
Draw some shapes on canvas ( on polyMesh3D divided), make sure do not cross/ exit the rectangle. When you are ready to make it tileable - Turn EDIT off (by clicking it), choose "S" SIGN - for Simple Brush, hold down TILDA "~" and drag>>> this makes the alpha tileable, as going to tile the canvas and this goes for all directions. When you are done, get out of edit mode (if you are), select "S" SimpleBrush and go grab the Mrgbzgrabber (what this thing does is grabs a depth map from your canvas and saves a black and white image in your texture panel). Click and drag outside canvas and this is gonna make an alpha for you. Then click on your Alpha Menu, select that alpha and Export it (as well you can manipulate it in PS, then import back to Z).
For custom alphas (or any other too), in order to NOT show edges around square of the edge of texture - got Alpha Menu - and play with values of the MIDVALUE and RF.
*Tip - if the image/alpha has medium grey edge, use MidValue to tweak the results. RF is for radial blur the (edges) of the texture/alpha.
Using Alpha (from texture file).
Go to texture panel, apply texture (texture ON under Tools Menu - Texture map), (Tools Menu - Maskin) mask by intensity - make sure you are in the highest divisions, so you get the most of the detail of your texture, then turn your texture OFF.
* tip - CTRL + Click on the mask will blur it. Alt + Click on mask will sharpen it.
You can either take a brush and start sculpting over the mask. Or go to Deformation Tab and Inflate, it will get a basic inflation of everything.
Creating an Alpha from Mask.
If you dont have your subtool UVed and you draw a mask, which now you want to create an ALPHA from:
Go to UV master (your model needs to be on SDiv 1 - the lowest). In UV Master (which is in Plugins - if you dont have it - find the plugin in Zbrush official website and install), click Unwrap (TO preview your Uvs in Zbrush - click under UV master menu - Flatten, to close the preview and go back to 3d model - click Unflatten.).
Go to Masking (under Tool menu) - click Create Alpha. Yu can now export it from Alpha Menu. It saves a 16 bit, Grey (no Rgb) image. Use .PSD format for easy tweaking in PS.
Displacement map is a texture map, so you need UVs to make one.
Put a texture map with texture you wanna displace (import the map file before that). Under Tool menu - Texture Map - New texture, chose it - Texture ON. Open Displacement map chose the same map BUT imported as ALPHA. Turn Displacement ON, slide intensity you can see the poping up of detail from displacement map, to see it applied you have to click Apply. Go to Texture Map and turn texture off. Its a good idea before applying displacement map to have Layer on recorder mode.