Actually the Trailer Hub Assembly # 8-247-50UC3-EZ that you referenced comes with a grease cap already with a removable rubber plug that will give you access to the zerk fitting of the spindle that will make lubing the bearings very easy.
I attached a link to the video you referenced as well. view full answer...
The part # 853-5907 Replacement Strap for Thule Quest Roof Mounted Cargo Bag is only on strap.
If you are needed 4 straps then you will need to order 4 straps. view full answer...