One way is if you have the watch compatible apps on your phone and then in the watch, open Google play and click on "Apps on your phone" - this will show you all the apps that can be installed on your watch and install them.
Second way is when you install an app on the phone, you can choose to install it on the watch as well. Same applies for watch only apps.
Hope this helps.
I understand where you are coming from. But I think the new way gives you more control over the that you want or not want to install on your watch.