Hi,
I understand that in order to build and rpm from an src.rpm file you need todo the following:
However, once I do that (in my case I'm trying to do this for bittorrent-3.4.2-
1.src.rpm)

All I find on my system is a directory called bittorrent-3.4.2 in /var/tmp witha series of files in.
I don't seem to find an rpm file there, although there is anrpm-tmp.58774 in /var/tmp


Any idea s how I get the rpm I was trying to build?

what does "man rpm" say about src rpm's?

A relatively quick way to find the binary rpm, if it was created, it to run (as root) updatedb, which updates the locatedb (a database of all installed files). Then use locate to find all files ending in .rpm. That will give you the file name and path to it's location.
In SuSE, when rpm's are built successfully, they are put in /usr/src/packages/RPMS/i386 or thereabouts. Gentoo probably does something similar.
It you still can't find the binary, you could try the older, yet still functional way to build an rpm from src.rpm. rpm -i to install the src.rpm. Cd to /usr/src/packages/SPEC, or wherever Gentoo puts the spec file, and run rpm -bb <filename>.spec from there, then look in the RPMS directory for the binary.

At the end of the rpmbuild output, it tells you that it wrote /<full path to file.rpm>...just use tab complete to rpm -Uvh /<path and rpm>.

Why are we talking about Gentoo? Gentoo doesn't even use RPMs. I suppose you could build one, if you were a developer and needed to package something for everybody else, but the normal manner of installing programs under Gentoo is to compile programs from source using a script called an ebuild. I don't even have rpm installed on my system, though I do have rpm2targz. Even the two packages that I have installed from pre-compiled binary for one or another reason are provided as tar.gz archives, not RPMs.

And no one claimed that ludwig W was using Gentoo anyway, so I am very confused as to why the distro is being referred to in any way .