In "Turn" you do not use M6 to get the offsets.
The "T" command is of two parts eg. T0101 (unlike "Mill" which is T +tool number)
The first 2 digits are the tool number from your tool table, the second two digits are the offests (also from the table) . Therefore you could have say tool 6 with offset 2. Don't ask me why, I don't know, but I assume this means that on an auto tool setter, you can select a tool number, and if all the offsets are the same, you can just use the same offset.
As Dave says, it works very well, I have a drill post mounted on my cross slide, for centre drilling - the x offset is common at 3.6267 inches. The other offset varies with the length of the drill, which I have set so that it arrives 0.05 inches from the work piece. The only difficulty is making sure there is nothing in the way, so after the T0404 or whatever, I do seperate G0Z0 and G0X0 to move it into position.
Reading your posts again - are you asking where to put the offsets - the answer is to enter your tools in the tool table, with the offsets.
It helps, of course, if you have a quick change fitting or similar, so all your offsets are fixed, once set.
You should be able to locate your X0Z0 position on your lathe, which is usually X0 - lathe centre and Z0 face of the workpiece (or perhaps the chuck face, which I use, because it is a permanent fixture). Set your most used tool to that position and then set the DRO's to zero. Enter this first tool with zero's as the offsets. Set your other tools to the same position and note the offsets on the DRO's and enter them into the table.
If you now choose a tool, using T0303 (or whatever) then G0X0Z0 should move all the tools to the same position.
If you have "home" switches fitted. You home the machine. A G54 offset then brings the machine to your normal X0 Z0 position, and your tool table takes care of the offset for all the tools. You can then write your GCode programs from the same "position" every time.
Jim