Totally agree. While you can definitely use a press on the UCA bushings it takes some careful blocking to make sure you don’t bend anything. I prefer using the homemade tool posted above even having a press, it’s much faster and it’s harder to damage the UCA that way.
Realistically, a tube like what you need for the tool is the best way to support the UCA to press the bushing, and if you’ve got that already then you’ve got most of what you need to make the tool!