winching under load
One of the objects of spooling under load is to get the wraps tight against each other. Just as important as getting them tight with the load.
When I spool it in, I have the Jeep anchored and pull another load to it. I don't think the actual weight of the load is as important as getting the wraps tight to each other. If they aren't tight against each other, then the next wrap can wedge down into the lower layer and cause kinks, broken strands, etc.
When I am spooling, I am not worrying about safety from a broken/flying cable. Not putting that kind of strain on it, just a few hundred pounds at most.
I stand in front of the winch and use my leg to hold slight pressure sideways against the wraps to insure it is tight against them. I have done it with a gloved hand also. Keep at least 6'-10' from the vehicle so there isn't any chance of getting pulled in. If you try and get them too tight the cable will slip up over the other wrap and then you have to spool out and back in. It is very important to be pulling staight in line with the winch so the cable wants to wind straight onto the center of the spool.
You can use a pole stuck into the ground below the winch line and use it as a lever against the line also.
When you get to the end of one layer and start the next, you will have a little trouble getting it to lay right. It will take a few times and you will get the knack of it.
When you get to the end of the cable it is a problem to get the cable tight without introducing slack and without warping whatever you are attaching it to. Again, takes some experience. A really heavy bungie works pretty good.
I would highly recommend installing a solenoid between the battery and the winch. That solenoid is energized either by an enable switch or when you push the winching control (takes a couple of diodes to do that). Otherwise, you have a fairly exposed hot lead that can get frayed and short out causing serious damage.
Now when you go to use it reality sets in. If you spool out too much line, you have just undone a good share of what you were so careful spooling. If you don't spool it back in correctly while actually using the winch you will get it wrapping back in incorrectly and creating the same problem as not spooling it correctly before.
Most of the problems come in from trying to retract the load too quickly. Don't forget to stop frequently and check the cable for spooling. If it isn't right (even, with no space between the wraps), back it off and spool it back in correclty before continuing. Hand pressure is adequate. One episode of really wedging the cable into a lower layer will convince you like nothing else.