The effect of using passive voice in the sentence "Once her hair and nails were done, Ellie's makeup was put on her by Tim" instead of the active voice in "Once Tim had finished Ellie's hair and nails, he put her makeup on" is that by using the passive voice, there is more emphasis on the actions (doing hair, nails, and makeup being put on) than the actor (Tim).
In the passive construction, the focus shifts from Tim, the one performing the actions, to the actions themselves and their completion, making it less clear who is responsible for those actions while also highlighting the processes involved.