Tech washes (Nikwax Tech Wash, Gear Aid Revivex Pro Cleaner) work better with waterproof laminates, which are sensitive to detergents. If you're just trying to get material off the face fabric, you could always wash the pants with no detergent or a small amount of regular detergent. I'd also recommend drying the pants in a tumble dryer on low as the heat helps revive the DWR on the fabric. However, always check your apparel's care label before washing/drying it.
I wash my waterproof/breathable clothes with a tech wash a couple times a year to help with performance as the sweat/oil buildup from use can decrease breathability, and the washing/drying helps revive the DWR. You should be able to find a tech wash for around $10, and imo it's worth it as it helps with the performance and lifetime durability of your gear.