If it helps, take the chrome end part off of the gun, it's just there to protect the tip on a flux core, completely unnecessary for function...
Yeah, I mostly just wing it, not really watching the puddle but it mostly works out. I'm used to stick welding though and have done more lately than I've done in a long time. If it helps, slow the wire speed to give yourself some time to think and get things going. Remember to concentrate on the bigger/thicker piece of metal, keep the wire there longer so you don't burn through. If you burn through, add wire speed or just stop and do a bunch of short welds to build up the hole and fill it in
Also, on that thin wall stuff, the low setting on the welder should be enough, with slow wire speed that will bring the heat up some and help the welds penetrate some and give yourself some time to see what is going on better.