Use what professionals use to speed up drying when they need to apply several coats on the same a day — Klean-Strip® Japan Drier.
Japan Drier is a special blend of lead-free drying agents which accelerate the drying ability of oil-based paints, oil-based enamels, varnishes and polyurethanes.
• Especially effective in high humidity or cool weather conditions
• Though Japan Drier appears purple, it will not affect the color of your coating; test first
• May be most suitable for use with darker paint colors; test first
• Do not use as a paint thinner
• The name refers to "japanning", a type of finish (usually a dark laquer) that was a European imitation for urushiol based Japanese lacquer