[ChevyTech]

When looking for a misfire in the shop the fist thing we do is put the scope on it, and watch the scope while power braking. This way we can see the firing voltage of the individual cylinders. If a cylinder varies from the others is shows. A low firing voltage can be from, a lack of compression on a cylinder, or a secondary ignition leak. A high firing voltage and you look for a open, plug wire. High firing voltage on all cylinders and you check the coil wire / cap. Low firing voltage on all cylinders and you suspect a weak coil.

Bad coil wires are common on these trucks. The inner core burns away. Look at both ends of the coil wire.

With no scope:
I would watch and listen for a spark jumping.
If I hear nothing, and it has a dead misfire, I would check one cylinder at a time like Speedy told you to do.
For random misfiring I would use a spray bottle to mist water on it and watch for sparks.

Head gaskets failing between cylinders can start out as a misfire, can cause pinging, progress to backfiring, cause overheating...

I will not throw parts at a problem with the low quality of parts being sold. You could be adding more problems making it harder to fix.

There has not bee enough of a description for me to take a guess at what the problem is.