That’s a very useful technique TVeyes. Thanks!
Great TVeyes. I was actually doing something similar for the matte paintings post, but hadn’t tried going this far. Thanks. This should solve the issues above. The tool is available. 
TVeyes, This is a very good atlernative, it seem to work very well, and its not so slow to do…
Just one question :after making the line tool, rotated the cup, put a marker, enabled projection master you say : CLICK THE MARKER
What do you mean? What key do you use, because in P.M I dont have markers option in my tool box…
When you add a marker (shortcut ‘m’) a little square dot appears on the canvas. You cannot see this dot while in Edit mode. When you drop the object with Projection Master (out of edit mode) scroll the cursor over the canvas to find the marker.
You can change Preferences : Marker : Marker Radius . This changes how close the cursor must be to the marker before it shows on the canvas. When you have found it click it with the object you want to place. When searching for a marker you can also look at the NoteBar at the top of the screen. It will show you info about the marker.
You need to use a marker to remember the cup’s position and rotation. You can change what the marker remembers when you click it by setting the various switches in the Marker palette.
I Never used before this ption… looks interestings… Thanks to share your knowledges!
well I know this is a pretty old thread but since this topic is important(I’ve searched the answer for some time and got nothing, until I stumbled upon it later) I’m going to post the answer here.
inorder to draw straight lines(horizontal, vertical or 45 diagonal) in zbrush canvas without going into projection master, hold down the shift key after you draw, not before. This will result in the startting bit of the line not quite perfect, but is the closest way I can get around to do stright line drawing.
Actually you do not have to even start a line. What you do is hold down your left mouse button, but do not move it, then press shift, then move your mouse while holding down the left mouse button, that will make you a perfectly straight line from start to finish, no ugly starter lines need apply. 
hope that helps for anyone who comes across this thread topic.
well thanks a lot sgtkoolaid that’s an excellent tip to know.
I tried it out 
I know this is an old thread but I would like to ask if is there a better way to do those lines , especially how to do them in masking , as seems work only outof masking and also the problem is you cannot decie the direction befoure starting drawind and most of the time I can’t get the right angle to start the line …