I'm considering a different approach this year.I have a Shaver 250 and had a real good heating season.Since the fire box is round,I may put a wire brush in an old electric drill and fasten it to a piece of plastic pipe so it will easily reach the back of the box and wire brush everything in sight.Step 2 will be to vacuum the fire box with an old shop Vacuum I keep for dirty jobs.Step3 will be to spray the fire box with WD-40.You may know,WD stands for water displacement and moisture makes rust.I buy it by the gallon for about $16 or $18.
As for the chimney,it is 5" diameter and insulated and screws together.If I can get the rain deflector off the top of it,I'll buy a 5" wire brush and brush it down as far as possible..My stove sits under the roof of my 25'x100' open sided wood shed.I'm doubtful my old 8" wire brush will squish down enough to fit inside the 5" pipe.
If none of the above works,I have no" plan B" yet but one way or another it shall be done.----------------------Shorman