You can get DIY slow-rise foam for the walls when cellulose settles and leaves a gap at the top:
https://tigerfoam.com/sprayfoaminsulation/order-products/spray-foam-kits/
I've personally only used the polyurethane stuff from HD so far:
https://www.homedepot.com/b/Building-Materials-Insulation-Spray-Foam-Insulation/N-5yc1vZbaxj
Caveats:
-This stuff will make you very sick from the off-gassing. Apply it with chemical mask in the springtime and leave windows open.
-It absolutely needs to be brought up to temp to rise. Put in bathtub for hours before.
-Distance from surface is important for chemicals to stick and mix: Too far away and it's like very expensive spray paint. Too close and it spatters and lumps.
-Expect over-spray which will be impossible to remove and will burn holes through finished materials.
-Prep first and use an entire kit at once. The nozzle will clog and the cans will cool down.