The only thing I want to add is a suggestion to try and avoid placing restrictions on how they will manifest. eg Don't say 'I need you to manifest like this' or 'like that' etc. Let them know they can manifest in any way they feel most comfortable with. This is literally how a manifestation spell in one of the CH Arts guidance books puts it.
When I read Muse's post, I imagine myself asking them, not telling them. Inviting / allowing, not instructing or pleading, if that makes sense. Leaving it open, not narrowing down the possibilities. I think we can easily get into a frame of mind where we kind of restrict possibilities, which I think creates a block.