Generally, black cohosh works better if taken over the course of a week or more at gradually increasing doses. It can be taken at higher doses in an attempt to get labor going but it's more effective if taken at smaller doses before hand (it's included in many labor-prep formulas)

. When my labor was slow with DS my midwives gave me extremely strong raspberry leaf tea with black and blue cohosh tinctures in it (one dropper of each). I did notice stronger contrx.
Strong RRL tea is good on a daily basis too...won't "induce" and may help once things do get going

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I've used evening primrose...does quite a bit to soften my cervix.
Nipple stimulation has worked for me too but I have to do it for a *looooong* time

. The contrx pick right up but if I stop before I'm in active labor...everything stops.