If you enter Foreign capital gains or losses in the foreign slip section, you should not enter that information again in the capital gains section. Make sure you use the box specifically labeled Foreign capital gains or losses, and it will be reported on Schedule 3 on line 174. Using the foreign slip section means you can include your foreign taxes paid, which will trigger the proper calculation of foreign tax credit as you said, if applicable. The PDF can be regenerated by going to File > Print Your Tax Return, so you can review your forms before you NETFILE or print and mail to the CRA.
