Everyone has problems with this, various way to protect light connections. I rarely use shrink wrap, have been known to silicone wire nuts but usually don't even do that anymore. I don't even bother sealing the boxes 100% weather tight. I usually use wire nuts, orient them so they are sitting upright, take the straw with penetrating spray and shoot a little in them after the connection and spray the inside of the box before closing. We use common steel boxes, 1/2 rolled poly will slip thru a 3/4 romex connector, makes shoving wires easy. You can take an awl and puncture it to insert a single wire if needed, for marker lite or LP lite, etc. The box keeps the studs from the fixture enclosed also. First pics are example, many variations of this theme.