I had to press in a CK just yesterday.
Took one length of threaded rod which comes in 1m length size M10(£5 or£6 i think :?) -reasonably thick so unlikely to deform or bend easily
Using trusty hacksaw i cut off 10" as neatly as i could
Placed 1 M10 nut and a cap nut on one end and tightened them together(effectively seals one end and the capnut means theres no ragged edge for you to catch your hand on), slid on a 50mm diameter(by about 4mm thick) washer
A 2nd washer then another M10 nut and tighten that single one till the cups are in place. You'll only be using a small spanner so when its fully home it will be evident and theres little chance of you over tightening it :?.
Obviously you place the cups in the frame roughly first. Plenty of grease and i mean plenty. its near as free so dont skimp. Ive usually found the cups sit in the headtube the first few mil,which makes things easier as you dont have to hold them and set up the press.
Cups placed in the few mil you slide the rod into the tube from the bottom with the double lock nuts and washer at the bottom, 2nd washer on the top add the nut and away you go.
This job is such an easy one and the making and use of the press is also as easy as pie that you will be surprised and have a 'man has discovered fire' moment when its done
One thing i would say to take note of and that is to make sure the rod press is central in the approximate middle of the tube. It keeps alignment dead straight and will do even if it is off a little bit *
* The fancy presses have cup adaptors that locate inside and over the top of each cup - much like a top hat washer. Its this that keeps the fancy ones exactly aligned.