Hi, here is my solution to do that:

Strings for controls are located in resources. Help link 

 ms-help://INFRAGISTICS_NETEN82CLR2_HELP/NetAdvantage_NETEN82CLR2/Win_NETEN82CLR2/WinElements/Win_Assembly_Resource_Strings.html

contains description of string you can translate.

I have a txt file which contains

MoreWindowsDlgClose Закрыть
MoreWindowsDlgCloseWindows Закрыть окно(а)
MdiCommandCloseWindows Закрыть все окна

where first word is Key of a string that need to be translated

" " splits translation(in this case - russian)

This file is located in resources.

then in code i have an util class which contains few methods

public static void LocalizeControls()
            {
                Infragistics.Shared.ResourceCustomizer cust = Infragistics.Win.UltraWinGrid.Resources.Customizer;
                StringReader r = new StringReader(Properties.Resources.translate);//this is txt file

                while (true)
                {
                    string line = r.ReadLine();
                    if (line != null)
                    {
                        KeyValuePair<string, string> val = GetKeyValue(line);
                        cust.SetCustomizedString(val.Key, val.Value);
                    }
                    else
                    {
                        break;
                    }

                }

                cust = Infragistics.Win.UltraWinTabbedMdi.Resources.Customizer;
                r = new StringReader(Properties.Resources.tabbedmdi);

                while (true)
                {
                    string line = r.ReadLine();
                    if (line != null)
                    {
                        KeyValuePair<string, string> val = GetKeyValue(line);
                        cust.SetCustomizedString(val.Key, val.Value);
                    }
                    else
                    {
                        break;
                    }

                }

                cust = Infragistics.Win.UltraWinToolbars.Resources.Customizer;
                r = new StringReader(Properties.Resources.toolbar);

                while (true)
                {
                    string line = r.ReadLine();
                    if (line != null)
                    {
                        KeyValuePair<string, string> val = GetKeyValue(line);
                        cust.SetCustomizedString(val.Key, val.Value);
                    }
                    else
                    {
                        break;
                    }

                }

                cust = Infragistics.Win.Misc.Resources.Customizer;
                r = new StringReader(Properties.Resources.misc);

                while (true)
                {
                    string line = r.ReadLine();
                    if (line != null)
                    {
                        KeyValuePair<string, string> val = GetKeyValue(line);
                        cust.SetCustomizedString(val.Key, val.Value);
                    }
                    else
                    {
                        break;
                    }

                }
            }


        }

        public static KeyValuePair<string, string> GetKeyValue(string line)
        {
            string key;
            string value;

                 key = line.Substring(0, line.IndexOf(" "));
                value = line.Substring(line.IndexOf(" ") + 1, line.Length - line.IndexOf(" ")-1);
          
            return new KeyValuePair<string, string>(key, value);
        }

when a program starts you call the LocalizeControls() method