We double towed with a 27' 5th wheel and a 18' Astro/150 Johnson (3480 lbs boat and trailer) for 8 years in the late '80s all over OK/AR/MO/TX/KS making some of the many COE lakes and rivers. The combo was 62' long.
As you mentioned I dropped the boat some where out of the way while we parked the trailer. Be sure and padlock the boat hitch and don't park in a position where someone can block you in. My boat trailer has a tongue wheel. I also used a
hitching guide
which is a big help when your alone.
I found the boat trailer pretty much tracks the trailer when going around a corner. The back of the camper swings out taking the boat trailer with it.
At a certain point while going around the corner you can crank the steering wheel extra to move the back of the trailer out which takes the boat trailer outside the campers tracks if the corner is short and sharp.
Backing other than a short distance in normal situations ie; camp grounds...forgets it.
Don't just turn down any street as it may be a dead end or a street you can't maneuver. Plan ahead.
And take it easy out on the road and forget about keeping up with the flow.
We actually tow triples (three trailers) in my state mostly in the summer months....one ton DRW/5th wheel trailer/ski boat/PWC trailer bringing up the rear.
Late fall hunting season the same DRW/5th wheel/horse trailer/ATV trailer.