This boils down to a series circuit; a power source in series with a lamp in series with a SPST switch made from two SPDT switches.
If you have a problem use an incand. test light rather than a voltmeter because there will be Phantom Voltages in this circuit and cheapie analog meters will be responding to the current rather than the voltage and so you will get different voltage readings on different voltage ranges because a Phantom Voltage acts like a current source rather than a voltage source.
Test your brand new SPDT switches with an ohmmeter before installing them. A wiring mistake can instantly clobber switch contacts. The switch wiper/common contact should have a different colored screw.
When you're wired up, if you want to avoid drama, substitute an incand. bulb in a pigtailed socket that is of equal wattage of the controlled bulb and use it for your closed switch contacts. Both bulbs should light dimly and slowly come up in brightness.
You have four combos to test. Full or no brightness indicates an error.
There are many ways for this to go wrong and only one way for it to go right so work slowly and deliberately because the odds are against the uninformed.
Test each step along the way if you'd like.
To paraphrase a saying having to do with marriage, "Work in haste, repent in leisure."