In my preparation I always ask; What in the text may be difficult for a non -believer or a new Christian to accept? Then if I was to address this what would I need to acknowledge and what angle would I take to deal with this 'defeater belief''? My aim is to help Christians think through the issue and address the concerns of others.
My hunch with Romans 8:29 is that the more affluent and western you are the more you believe you are in control and the more sceptical you are of ultimate claims/authority. The idea that God is in control and will direct the world to His purposes is extremely confronting and is a 'defeater belief'.
So acknowledge the power that affluence gives you but point out that in regards to ultimate questions of control we are all in the same boat and that it is a delusion to suggest otherwise.
Then consider the other option: What if the God didn’t “horizon beforehand” (foreknow) the people he wanted to call people to himself and it was totally our choice? That would make some people better than others more intelligent more gifted/educated at hearing God ETC (also a temptation of the affluent)–the risk -loss of Grace alone.
I think it comes down to a matter of reasonable trust-is their evidence that God cares for this world and loves it –yes in the death of his son 8:31-37 do we trust God?