Workshop(s) for application to Marie Curie postdoctoral Fellowships (formerly IIF, IEF and IOF, now just IF)
Typically, universities organise these workshops (training events) for their own faculty, possibly in collaboration with commercial companies that provide this kind of training. This is the case not only for Marie Curie fellowships, but for all kinds of EU Horizon 2020 funding opportunities.

Contact the research support people from your own university and ask if they are planning to organise such workshops. Most likely, it would be free for you. Your university would cover the expenses.