It's great that the Rad Mini 4 has protective liners between the tire and tube, but would it help to spray in tire sealant? Or would that be a waste of time?
Since when did Rad start putting protective tire liners in as shipped RM4s? Mine didn't come with liners, I added Mr Tuffys after getting three flats in the first week.
Most canned "spray in" tire sealants are designed for temporary emergency inflation and sealing and any tube they're use in should usually be replaced when you get home (check the specific recommendations on the can). Sometimes you can get away with letting all the chemical propellant out of the tire, patching the tube, and reinflating using real air.
The two most commonly used and highly rated bike tire sealants are both "squeeze in" types from Slime or Stans, again, follow each manufacturers recommendations.