I would use shotgun pellets, 9 shot. Scatter them around and it will drive the detectors crazy. Enough thing is toss pull tabs from cans and toss them around. Basically make the area look like its a trash dump and most detectorists will get frustrated and move on. If they know something good is buried there they may stick around longer but finding endless pull tabs, cans, other metallic trash, will help them lose interest. Also burry some stuff deeper, make them dig for trash and that will frustrate them
If you burry your goodies 3+ feet deep you should be safe from the majority of detectors which won't reach that deep.
I have 2 detectors, one for relics and one for small gold. Two completely different rigs, both alert to just about every metallic object and they will also alert to rusted out fish hooks. The hooks are very frustrating because the rig alerts very loud but as you dig, the hook rust pile will disburse and the signal will disappear.

I'm a novice with these machines but they are high end rigs that were not cheap.