We've found that they're sometimes harder to apply and buff off compared to other waxes we've experienced.
I don't think there is any wax out there that will resist stone chips, and with regards to application of Zymol - we've found it best to work on a panel at a time, leaving the wax for a couple of minutes and then buffing off. This may not work the best for everyone, but we have found this to work well for us when using Zymol.
The smearing is caused by the oils and solvents in the wax not having enough time to evaporate properly if you apply it too thickly. This can be minimised by applying a much thinner layer and allowing more time between coats.
As previously mentioned, whilst the wax will offer a high level of protection against the elements, we don't know of any wax that will stop stone chips - to prevent these you'd probably have to look at some sort of paint sheild.