Somewhat antiquated photo (now I use RTD). I don't like the size of my crosses (that's 3/4" with a 1/2" NPT bushing gooped into it) but that was all I could find local. I would personally suggest the 3/8" crosses if you are buying from McMaster anyway.
I have some plugs for the dP connectors (the small tubing) that I made with a glass rod stuck inside the vinyl tubing. So I can move the temp probes around if I don't need to take pressure measurements.
Also be aware that you have to take measurements of the system with just a straight piece of tubing connecting the barbs and then cut that tubing in half and mount your wb or rad. Always use a standard length of tubing and make sure that everything is flat and straight. You then subtract the tube only numbers and you have the dP vs flow curve for your part of interest. Spend the time making those measurements on just the tubing and you'll get good with the instruments. The way Ben has his setup drawn there will be a 180 degree bend in the tube, which is not good for doing this measurement because the bend affects the dP of the tube.