The crud is most likely the left over plumbers thread seal from the old one.  Just wipe it off.  If it is white bubbly hard residue that could have been corrosion from a leak.  Scrap it off.

I would flush out your tank with a garden hose.  I used a female plastic hose mend from HD and attached a length of 3/4 clear tube I had lying around so I could get the water inside the tank.  As I was flushing the tank I took another length of the tube and created a syphen to vaccume the bottom out (worked like a charm) I was amazed how much sand came out when I did that.

When your ready to reinstall the new anode just coat it with plumbers thread seal and tighten like a spark plug  No need to crank it with all your might.

I use the bottle brush style wire brushes and reach into the flame chamber and then blow compressed air to get all the rust out of there.

I gently brush all the fittings and connections and then air gun everything off.  I do the same for the Refer.

The first light of the season is tough run the stove for a few minutes to get the propane thru the lines.