The problem is that I find it difficult to click both buttons at the same time. I usually end up clicking one or the other, which typically throws off the focus and undoes the 'copy' (so the stuff I want to paste is no longer in the X11 clipboard).
(Yes, this is exactly the sort of thing that drives me insane.)
The other day while I was working on a desktop computer, I ran some google searches trying to find a solution, and I found out that if you do shift-numlock and then a 5 on the number pad, that amounts to a middle-click (then you have to do shift-numlock again to resume normal use of the number pad).
(Have you seen the problem with this solution yet?)
I was eager to get home to try this on my laptop, only to feel a crushing humiliation to realize that my laptop does not in fact have a dedicated number pad. (There's a special function key which can convert about a dozen keys on the keyboard into a number pad, but the trick doesn't work on my laptop.)
But then I realized that I could use xmodmap along with the key-handling feature of my window manager. The xmodmap 'pointer' command lets you remap your mouse keys in real time (a left-handed person can use this to make his/her mouse work correctly). If I tell my window manager that control-alt-9 means
xmodmap -e 'pointer = 1 3 2'and that control-alt-0 means
xmodmap -e 'pointer = 1 2 3', then I can highlight some text (to copy), do control-alt-9, and do a hard-to-screw-up right-click to paste (and then control-alt-0 to resume normal right-click operation).
To do this in fluxbox, just add these two lines to ~/.fluxbox/keys:
Control Mod1 9 :ExecCommand xmodmap -e 'pointer = 1 3 2'
Control Mod1 0 :ExecCommand xmodmap -e 'pointer = 1 2 3'