Yup, melt the lube and pour it in. That's how Harry Pope said to fill his custom bullet lube tool. Eliminates air pockets.
I aim a 40 watt heat lamp at my 450s for 20 minutes or so before I start a session. That softens the lube so it flows much more easily. Some people buy special "heater plates" to mount the lubrisizer on, but I'm not that anal.
Yes, that stuff is NRA 50-50, and it can't "dry out" because it has no solvents in it. As I posted, I'm using up some that my Dad bought almost 50 years ago.