The rash of poison ivy is an allergic reaction to urushiol, an oil released by the plant.
Both benzethonium chloride and salicylic acid in solution may help to remove urushiol from the skin, but neither will help to counter the rash once the allergic reaction has begun. I cannot imagine any benefit from applying clear nail polish to the allergic rash.
Here is more information about poison ivy treatment.
Poison ivy/oak dermatitis usually resolves within one to three weeks without treatment.
To remove the urushiol, the plant oil that triggers the rash, the following is suggested, if possible within 10 minutes to four hours of exposure:
First, use rubbing alcohol to clean the exposed areas. Ivy Cleanse Towelettes may be used in place of rubbing alcohol.
Second, use warm water to wash the exposed areas (no soap yet, otherwise you risk moving the urushiol around the body).
Third, shower with warm water and soap (a soap with colloidal oatmeal, such as Aveeno, may help to counter itch, while Zanfel soap or Tecnu Extreme Poison Ivy Scrub helps some patients).
Wearing heavy-duty vinyl gloves (the urushiol may seep through latex or rubber gloves), wipe everything that was worn with exposure (e.g., clothes, shoes, tools) with rubbing alcohol and water. You may also hot wash all clothes, shoes, bedding, etc.
Topical therapies to counter itch may include: oatmeal baths (e.g., Aveeno Soothing Bath Treatment); calamine lotion or Aveeno Calamine & Pramoxine Anti-Itch Cream (pramoxine is a topical anesthetic to numb the skin); cool wet compresses. Once the blisters begin to weep fluid, consider aluminum acetate astringents (e.g., Burrow's solution and Domeboro). Over-the-counter, low potency topical steroid creams are of little benefit (most patients require a high-potency steroid cream or tablet prescription or a steroid injection in the first few days of symptoms to gain relief via anti-inflammatory steroids).
In some patients, use of the following may worsen the rash (e.g., allergy to specific components): topical antihistamine creams or lotions; benzocaine-containing anesthetics; topical neomycin (e.g., in Neosporin) or bacitracin.
Oral therapies: Besides prescription oral anti-inflammatory steroids, over-the-counter or prescription antihistamines help to stop the allergic reaction and relieve itch. Consider sedating Benadryl if the itch disrupts sleep versus non-sedating Claritin or Zyrtec. Note that antibiotics are not helpful unless the patient also develops a bacterial infection (e.g., from scratching the skin open).