Umbraco site version 7.7.4, using uSkinned

Client wants to exclude a load of random pages from the sitemap, around 600 altogether. There is no common document type - a few of these, a few of those. I was wondering was there a straightforward way of doing this via the database, but my knowledge of the schema is a bit lacking. I think I have figured out the relevant tables:

[cmsPropertyType] where Alias is umbracoNaviHide = 278, say

join to [cmsPropertyData] where propertytypeid = 278 

 join to [cmsDocument] where nodeId = 10127 and newest = 1 - join on versionId

(Please excuse above, I haven't actually written any SQL yet, just figuring out how they all fit together)

But then I still need all the node Ids - if we are going to have to scrounge up all the node Ids we may as well just change the setting in the admin area. However we do have the URLs they want to exclude - would there be an easy way to use the URLs instead of the node Id?

Or is there a package which would allow bulk updates like this?

I am only sussing out feasability at this stage so really just wondering if it's realistic at all.

Thanks