How do churches (specifically WELS) proselytize while barring all forms of fellowship?

So my question is about churches (or more specifically the Wisconsin Evangelical Lutheran Church) which bar all forms of fellowship (to include prayer) unless all points of doctrine are agreed upon. For example, two Lutherans, one from WELS and one from LCMS, have very similar doctrines. The LCMS Lutheran believes in limited fellowship, but will pray with non LCMS Lutherans. The WELS Lutheran will not pray with the LCMS Lutheran however. This makes me wonder: How is it possible to help someone grow in the faith when you cannot even pray with a person until you agree on all points of doctrine? How can they even learn all points of expected doctrine without having a community they are in fellowship with? Do they make an exception when someone is growing in the faith? Do they not bring people to worship services until they're ready to be baptised - and agree to believe all points of doctrine? (So do they discourage parishioners from bringing friends to church?)