K-it takes some practice and some skill but muscle testing is pretty easy.

If someone were to hold their arm straight out to their side and you told them to resist while you pushed down (not to fight you but just to try to hold arm still)...

So you do that and then give them a known poison to hold (in bottle etc is fine). Some cleaning product, deet, coke etc

Test again while they are holding.

If they test weaker then give them a bottle of mineral water to hold.

If they test strong then you are ready to move forward.

You need to be able to get clear responses or else what the hell are you getting?

I would go further and ask their name and test (should be strong)
Then ask them to lie and ask their name (should be weak)

Have them think of a positrive memory-test
a negative memory and then test

Know toxin/poison
Known something good (mineral water)
Name
Lie
positive memory
negative memory

If you get clear responses all the way (correct in what is strong and weak) you should be able to trust any results you get when they hold a food for example.

If not getting clear answers then there is a problem. Either you the tester or them. On line I'm not going to go into it all (there could be polarity reversal, toxins that are mixing them up they could be 'switched' etc) The tester could be switched etc too

But if getting clear results with toxin/good for you, truth/lie, +/- memory then you should be good to go.

Hold a loaf or slice of whole wheat bread and test.

Have them say "I love you" test and " I hate you" and test if you want to cratch the surface of where this can go.