Acid brushes for tubular gluing are cheap and perfect for the job. Available at your hardware store.
Acid Brushes - MSC Industrial Supply
Glue Brush Set - 6 Piece at Menards®
13 Unbelievable Acid Brush for 2023
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6 Paste Flux & Acid BRUSHES 100% Horsehair Stiff Bristle Applicator for Flux Acid Glue Oil Shop Aplication Metal Tube 6 1/4 X 3/8 Brush - New Zealand
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Acid Brushes: Small but Important Details – Lost Art Press
Mechanical Mondays: Gluing Tubular Cyclocross Tires - Cyclocross Magazine - Cyclocross and Gravel News, Races, Bikes, Media
Adhesive Systems AS203 Nickel Anti Seize - Chemical Concepts