No matter what i do I always get lumps...Please someone help
Sift your PS.....and let the MMF sit overnight. Those are the only tips I have.
I also sift the PS and use my Kitchen Aid stand mixer with powdered sugar on bottom, melted marshmallows, extracts and salt water next and then shortening on top. Using a greased dough hook, once it pulls together I get it out of there and then finish kneading on the counter. HTH
If you're talking about little hard sugar rocks in your finished MMF......
I've had this happen when I added refrigerated powdered sugar to the melted hot marshmallows.