Some thoughts:
Most other dating methods are uncalibrated. They work solely on the decay rates of the minerals.
An interesting confirmation of the accuracy of Ar-Ar dating (an isochron method based on the K-Ar system, although isochrons are seldom plotted) is nailing a 79 AD eruption of Vesuvius within 7 years, even though the samples contained "excess argon" (daughter product that was present at solidfication, beloved of creationists).
40Ar/39Ar Dating into the Historical Realm: Calibration Against Pliny the Younger.
Furthermore, some dating methods are isochon dating methods, which utilize isotope ratios in addition to individual decay rates, enabling a further cross-check.
And isochron methods do
not presume that there was zero daughter isotope present at solidification. See above.
The vast majority of dating methods used today have some kind of cross-check built into them, and those that don't (e.g. plain vanilla K-Ar) are essentially never reported unless they are confirmed by some other method. The most popular methods today are based on the U-Pb-Th system (partly because the decay rate of U is known more precisely thatn any other). The most popular method in this system is concordia-discordia, which is not an isochron method but is instead a simulatanous use of two different methods. It can often provide a valid age even if the system was not closed since solidification, and indicates when a valid age is not available. (It does involve the premise that there was essentially zero daughter Pb at solidification, but that is justified because it's done only on minerals that reject Pb incredibly well at solidification).
To get a "young earth" from dating methods, you not only have to explain why you think they're wrong, but why you think they're all wrong, since they confirm each other (with a few exceptions in experimental cases). Not just why you feel that they're wrong, but how dating methods using isotopes with different half-lives all come up with the same amount that you consider to be "wrong".
Not just different half-lives; totally different and independent methods of decay (alpha, beta, electron capture). Something that affects beta decay will typically have no effect on alpha decay.
Some tables of concordant dates:
Consistent Radiometric datesRadiometric Dating
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