Personally I have a USB drive with Ventou and have been using that for a long time.

But before that I just did a dd. Although I seem to remember someone doing a benchmark and realizing that piping the file was faster. Here's what I mean by that:

In bash you have the echo command which prints text:

echo "Hello"

Will print Hello.

In bash you can send the output of a command to a file, so:

echo "Hello" > hello.txt

Will write Hello in the hello.txt file.

In bash you can use the cat command to read files:

cat hello.txt

Will print the Hello we wrote in that file earlier.

In Linux drives are files, so if your USB drive is in /dev/sdb (DON'T JUST BLINDLY COPY THIS) you can create an image of it like so:

cat /dev/sdb > usb.iso

But also the devices are writable, so you can flash an image to a disk by doing it the other way around:

cat image.iso > /dev/sdb