Flux core (innershield) wire vs. solid. Flux core generally uses less voltage/amps than the same size in solid. This means you should turn the machine down. Polarity is usually also different between the two. Solid= work lead to - & gun to +. You would switch for flux core most of the time, gun to -. Knurled v-groove rollers work better for flux core as stated above. Smooth v-groove for solid. Flux core uses a longer wire stickout than solid. About 1" for fux, 1/2" for solid. Keep the nozzle on or get a flux core nozzle when running flux core to protect the diffuser. I like splatter spray more than nozzle dip. They sell it at GTS-Welco. No need to soak it, just spray it once in awhile. Get yourself a bunch of extra tips & also a torch tip cleaner to clean your mig tips. No reason to throw them away until they get worn. Don't be afraid to remove the nozzle & clean it with pliers or a screwdriver.

When changing rolls of wire it's a good idea to blow out the gun with compressed air.

The above are just generalizations. Check the wire mfg. specs & the door chart is always a good starting point.