While I don't use Osmocote for my Neps,
I know many people have for other plants.
I would say as general advice, that if a plant has no roots developed yet,
that is isn't a good idea to give it much / if any fertilizer at all.
For most plants, it will lead to rotting death otherwise.
For most my plants, I wait until a decent root system is developed before fertilizing
and I would recommend you do the same.
Be sure to use a mix that is 1/2-1/4 or less of the normal concentration.
(Often I only recommend a trace amount, as the plant can only absorb that much anyway,
and is safer to do until the plant tells you how it feels about it. Only then should you consider applying a more concentrated amount.)
Keep in mind that the goal isn't to see how much you can apply before the plant is killed...
so this tends to be a case of less-is-more, especially for those experimenting for the first time.
Good Luck!