Putting large pics in so you can see what's going on. Shouldn't have to jam the connectors in, but most of the time they'll need to be persuaded to make it all the way in.
Inserted up to the insulation crimp.
Using Needle nose pliers to gentley wiggle and force them in a bit. with 20AWG and silicone wire this is the hardest part.
Went about as far as possible with the needle nose.
small standard electronics screwdriver will help a lot here.
99% in, just need to finish installing them with another tool...
Back end of an Xacto blade works well. My advise here is to push the connector up against something so the blade doesn't snap and enter your hand.
Final check is to see that the connector didn't warp during the process, is fully inserted, and is locked in place.