Ok. So i noticed that if you have any content ratings settings applied via any policies it forces a prompt of the login box. I had this issue with student ipads earlier this week. Once i turned off any content restrictions, silent installation worked fine. Aside from that the processes is pretty straightforward.
-'purchase' the app on the app store in itunes on mac or pc. Once it is showing in purchased apps it should be pushable silently.
-find app listing in meraki and add it to your lists. I used tags so i could make sure to install it on specific devices. if you dont tag it, it will install on all IOS devices within the System Manager network.
-if you havent signed in on the ios device, it is going to prompt for an account on the first app push, but shouldn't afterward. I had already grabbed one app off the store when i started pushing out apps, so itunes information was already in the device. The only way you are going to be able to push apps is to have it signed into an account. If you have any intention of letting people use their own AppleIDs, there is little control you can put over what they install or uninstall. With Apple Configurator, you could setup layered supervision which would allow you to put the apps you want to on the ipad for company purposes, but also allow your employees to sign into the device with their account. At this time, it can only be done via Apple Configurator.
The new OS X Server is suppose to bring in some wireless supervision, but i haven't gotten to toy with it. If you have paid apps you want the users to have, Apple is suppose to change their Licensing model soon to make it a lease-based system. You lease a license of a paid app to the users and can revoke it later to give it to another person.