ProjectWise wep API (REST)

I am creating an application where I use the ProjectWise web API (REST) version 2.4.

I find the documentation quite sparse. I need help in two specific areas:

1) Saved searches

/PW_WSG/SavedSearchDefinition gives me all instances of saved searches, but I don't know how to "execute" a search.

2) Document custom properties

I need a way to get all the custom properties (the environment meta data) for a given document.

Can anybody help with these issues?