When working on a car, body filler can be an essential tool for smoothing out any imperfections. But it’s not as simple as just slapping some filler into place; you need to use a primer first. Primer helps the body filler adhere better and gives it something to bond with so that it will stay in place once applied. It also prevents corrosion and oxidation which can reduce the life of your repair job significantly. A good primer should have strong adhesion qualities while still being easy enough to sand off if needed. When applying primer, make sure to follow all safety precautions like wearing eye protection and using proper ventilation since these products may contain hazardous chemicals that could cause harm when inhaled or exposed to skin for too long. Once you apply your primer correctly, allow plenty of time for it to dry before beginning work with body filler - usually about 24 hours is recommended - then you’ll be ready for a great finish on whatever project you’re tackling!