Thanks for your reply.  Is there a way to get the rights back from a folder as a list of trustees/groups and loop through them?

To get the access rights assigned directly on an entry (a folder or a document), call EntrySecurity.GetAccessRules(true, false):

public static void ReportEntryAccessRights(Session session, int entryId)
{
    EntryInfo entryInfo = Entry.GetEntryInfo(entryId, session);
    EntrySecurity entrySec = entryInfo.GetAccessControl();

    bool includeExplicit = true; // Include ACEs assigned directly on this entry
    bool includeInherited = false; // Include ACEs inherited from a parent folder

    Console.WriteLine($"Reading security for {entryInfo.Path}");

    foreach (EntryAccessRule rule in entrySec.GetAccessRules(includeExplicit, includeInherited))
    {
        try
        {
            Console.WriteLine($"Account: {rule.AccountReference.AccountName}");
            Console.WriteLine($"  Allow/Deny: {rule.AccessControlType}");
            Console.WriteLine($"  Scope: {rule.EntryAccessScope}");
            Console.WriteLine($"  Rights: {rule.EntryRights}");
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }
    }
}

If you are looking to get the entries within the folder and find security on them, use FolderInfo.OpenFolderListing to get the child entries, then use that list of IDs to lookup the security on each entry:

public static List<int> GetChildEntries(Session session, int folderId)
{
    FolderInfo folder = Folder.GetFolderInfo(folderId, session);

    List<int> childEntryIds = new List<int>();

    EntryListingSettings settings = new EntryListingSettings();
    settings.AddColumn(SystemColumn.Id);
    using (FolderListing listing = folder.OpenFolderListing(settings))
    {
        foreach (var row in listing)
        {
            int entryId = (int)row[SystemColumn.Id];
            childEntryIds.Add(entryId);
        }
    }

    return childEntryIds;
}