If you can, be sure the rod you get (or the tool) has acme thread on it. The reason is, normal threaded rods will allow the nut and washer stack to tilt, which can make it hard to press the cups in straight. If you don't press them in straight, you risk damaging the cups and/or ovalizing the head tube (which can't be fixed).

You can do it with normal rod, it's just a lot more of a pain. This is why higher end presses have acme thread, and then the drifts (that actually press on the cups) are thick: so they don't tilt on the rod. You can get away with no acme thread if the drifts fit the rod snugly and are thick. A stack of washers won't do that.

Personally, I'd buy one like this: https://www.amazon.com/Bikehand-Bicycle-Headset-Install-YC-107/dp/B008121634/ (or just find a friend to borrow a Park from).