If you do not have X homing this is what I would do.
Offset a master tool, ex. tool No. 1.
Then offset the other three tools.
Record the differences between the master tool and the other tools.
Next time you turn on the machine (without homing) you need to set the offsets for the master tool by making trial cuts. Then you just enter the tool offsets for the other three tools, by adding the differences you recorded before with respect to the master tool. In this way you only need to set the master tool every time you turn on the machine.
The process I just mentioned may be done in other ways, but the process will be fundamentally the same. For example you can move the master tool to 0,0. Then use Part Zero X and Z and you are set. It is very important that the other three tools are set correctly with respect to the master tool so you do not have to mess with them every time you turn on the machine.
If you had accurate homing you would do this process just the first time, so its worth the effort to do install home switches.