A bit similar to Arcadia once i put DD in her cot i'd still have my arm really close to her (kind of slide in under the cover so she still feels my arm and can smell me), then once she seems settled in her bed i'd remove it.

I think you mentioned a comforter also, if you haven't already... it's great to tuck it into your top for a day or so and get your smell on it, then try using this at sleep times. DS will love to smell you. But comforters can take some time to become favourites, DD is 8 months and just starting to show an interest/comfort in it.