Putting a lock strip style windshield gasket in is actually slightly easier than the solid type since they are a touch looser.
It takes some talent to install by yourself but I do all mine that way.
It sounds more complicated than it is, but:
You want to use nice cheap/rough cotton clothesline (not the kind that will give you rope burn, the kind that will just rip your skin right off, none of that nice slippery synthetic stuff) and run that around the window gasket pinch weld channel, overlap the two ends a few feet at the bottom and leave the tails hang out.
I usually do this with a full hank of rope so one tail is WAY long, I set the window in place and set the bottom over the pinch weld, then I take that extra long loose end, loop it over and outside the top of the window (you are inside the truck) I then tie a big burly knot in it so that when you pull on it from the inside, it jams up again the window and body and by pulling down and in, you force the window down and in.
Now you need three hands so I wrap that extra rope with the knot on it around my neck, or arm, or leg, or teeth, or whatever you can pull down with some force on it with while using my other two hands to pull the rope tails and coax the gasket over the lip with.
Works great, might look a little funny but they pop right into place.

KR