I doubt it's the lab techs that are in short supply. It's probably the consumables and reagents that go into the test that are out of stock. Lab procedures scale pretty well (to an extent - not the scale of the pandemic). Lab work is often feast or famine in terms of sample volume. During normal times, spikes usually just means the folks running the assays will be particularly busy.

With all that said, there's still a lot of specialized skills required to competently run these tests. You'd still need significant training if starting from nothing. But there are enough un/underemployed lab techs out there that finding more techs won't be the bottleneck.