Hi,
The instructions look good to me- although I personally don't use the Default Domain policy for software deployments (personal preference).
I have a hidden shared directory on the file server that I put all the MSI files in for deployment (It's setup with \users having readonly access, and SYSTEM and Domain Admins with full control).
gpupdate /force will certainly cause the machine to do a complete policy refresh, but it shouldn't be necessary (unless you are running wireless where the network sometimes isn't ready by the time the machine comes to update at boot)
This system of application deployment is my favourite method and I'd be happy to discuss it with you in more detail.
Gareth