I believe complete sealing of all wall headers is important, and do it without fail. It is made easier for me by installation of safe access, secure decking and lighting. I dig down even through deep loose-fill, in the rare instance where a wise home owner now wants access, as to deal with defective attic ventilation.
Caulking is the usual sealing method, and I have tried everything offered. Gun-applied foam is fast. I have consumed several Sharpshooter X guns at replacement cost up to $50, and lots of regretted volatile cleaner, yes, claimed exempt VOC, making messes and still not preserving the life of a gun that might be idle for a month. I think a frozen gun is not worth the time of repair, with accelerating degradation. Tube-dispensed caulk goes fast with poor volume control, will not bridge gaps larger than 1/8", and is a tracking hazard on shoes.
I always have flexible grout in hand in a one-pound tub, for interior work as in a can light annulus. This fingertip application is tedious, but I have not lost a couple hours readying a foam gun. The wetter the surface at application, even down into vertical surfaces, the better. The grout must be handled as paste, but dilutes and is carried into water, like platelets. Little material is needed to bridge a gap. Go back sometimes with repeat quick application. I won't likely step on a treated wall header, in the fifteen minutes before material is dry. Anything tracked could be removed by vacuum or damp sponge.
The flexible grout is a plaster crack repair material, and much more. I advocate for it to be available everywhere, at my plaster repair blog, offering free samples with promise of impending use and posted report of the experience. I extend the same offer to weatherization advocates and contractors. In weatherization, we must experiment with the packaging. Perhaps the wetting might be by brush of material at paint consistency. Hand-packing paste into an Albion bulk gun was a time loser, with the same overfill problems that are wasteful of squeezed tube caulk. Availability for weatherization might come faster if the material is also used to seal joints of HVAC ducts. Goop presently used on ducts needlessly is not water based, is horribly sticky, and is awful on equipment and clothing. An elbow might not be permanently ruined for reuse, if sealed with grout, not goop, at its alignment seams. Longitudinal pipe seams, aiming up, would be easy to grout.
I am aided sometimes by ability to bag and reset loose fill insulation, using 55-gallon drum liners, always several for trash or for transfer, on a job. With only a few inches of loose fill, just brush away.