I target feed reef roids in tank water and a drop of aminos with a little bit of mysis mixed in for the fish/crabs. I target feed directly via pipette.
Yes. My LFS rents a PAR meter. Check with yours too. The local reefing club (if you have one) may do this too.
But even with the meter, I mostly just move them around until I find a good spot. Knowing my PAR just gives a good baseline. I have a frag I’d Red Mauls (or similar - I’m awful with the names) that is thriving in 175-200 territory. The rest are down under 100.