Here's a step-by-step guide:

1. Safety Precautions:

• Wear appropriate safety gear, including gloves and eye protection, to prevent burns and splinters. 
• Work in a well-ventilated area, especially if dealing with old varnish that may contain lead or other harmful substances. 
• Use a heat gun with a low to medium setting initially, gradually increasing if needed. 
• Don't hold the heat gun in one spot for too long to prevent scorching. 
• Have a fire extinguisher or water source nearby. 

2. Prepare the Surface:

• Remove any hardware or items that might be damaged by the heat, according to a DIY resource. 
• Cover any areas that cannot be removed with heat-resistant masking tape. 

3. Heat and Scrape:

• Hold the heat gun a few inches away from the surface at a 45-degree angle. 
• Move the heat gun slowly and steadily over a small area, allowing the varnish to soften and bubble. 
• Once the varnish starts to soften and bubble, use a scraper or putty knife to lift and remove it. 
• Work in small sections, overlapping slightly as you move across the surface. 
• Be careful not to overheat the wood or allow the varnish to smoke. 

4. Clean the Surface:

• After removing the bulk of the varnish, use a scraper or sandpaper to remove any remaining residue or stubborn spots. 
• If any stain remains, you may need to use a chemical stripper or sanding to remove it. 
• Once the surface is clean, it's ready for refinishing. 

Sand the wood thoroughly to create a smooth surface for the varnish to adhere to.

Clean the wood to remove dust, dirt, or any residue from sanding or previous coatings.

2. Apply varnish:

Stir the varnish gently before applying.

Use a brush, roller, or spray applicator to apply thin, even coats of varnish, following the direction of the wood grain.

Tip-off the varnish after each application by lightly dragging the tips of a brush across the wet varnish.

3. Dry and sand:

Allow the varnish to dry completely according to the manufacturer's instructions.

Lightly sand the dried varnish with fine grit sandpaper before applying additional coats.

4. Repeat and finalize:

Apply additional coats of varnish, following the same process of application, drying, and sanding.

Once you have achieved the desired finish, allow the final coat to dry completely.