Painting trim is a Pain! I know because I have! So I'll give you some easy steps to succsess!
1. Sand all your trim before you start painting. You can use regular sand paper, sanding blocks, or other sanding materials. Make sure you get in all the crevices!
2. Use de-glosser! You can find this at Lowes, Home Depot, or any other hardware store. Put the deglosser straight on the trim that's already been sanded.
3. Add Floe-Trol to your paint before putting it on! Floe-Trol comes in an orange bottle and you can also find it at most hardware stores.
Once you have done all these things you are ready to paint! Good luck and comment at the bottom to tell me how it worked!