.... For me nothing has worked better than Loc-Line It makes it easy to adjust the final length by adding or removing sections. .... Loc-Line has a valve you can use to turn on & off the flow.
Ok, that is one vote for Loc-Line and a confirmation that it works.
As for using some sort of tubing to get out on the machine head and going with LocLine from there down to the spindle That works, but if the flexible ball joints in the adjustable hose will accommodate being extended that far, it would be cheaper and faster to just use the flexible line straight from the column to the spindle. Got any experience on how far that flexible line can be hung out there?
If I have to use some sort of hose to first get out to the head before using the LocLine, I think the pressure is low enough that most anything would suffice so long as the coolant does not react with it. but I might have some "burst proof" faucet hose that has the stainless steel braid over the hose. That would be fairly abrasion and cut resistant.
Loc-line will not support itself very well over that length probably in the 12" range or perhaps a bit more. It's amazing just how resistant that stuff is to chips, grit etc. About the only thing I have ever had actually ruin a link or 2 is once in a while on a lathe a purple hot long string will insist on "Hot Knife" cutting. But still that isn't a big problem just pop out the bad piece & right back together. After very long periods (5 years or more) of soluable oil Loc-Line seems to harden a bit & may begin to split on the female end of the links..
If I were going to dispense straight from the port shown on your mill I'd probably plumb in a solenoid valve for the on/off with a switch in a handier location than the 1/4 turn valve.
you can probably fabricate something from heavy, possibly music wire, (think jib boom) to help support the lock line for distance. Also if Loc-Line is anchored higher it will stay where you want it better over a longer distance.
It can get complicated to design something that will still allow you to swing the head to far right & left. Extend the over arm way out etc. You almost need a long flexable tube between your existing valve & a hard mount or strong magnet mount as close your work as possible.
I tried a magnet mount sitting on the vise or table near the work. Sort of ok for drilling etc but sucks for milling work because the flow will not stay on the tool. Then there is cleaning the chips off the magnet. EEEeeeeek.
Most coolant pumps have very low pressure but pretty good volume. I use Clear vinyl tubing you can buy for a few cents per foot as long as I can heep it somewhat away from really hot flying curls.. It too will resist most anything a milling machine will throw at it. It hardenes & gets stiff with age but is really cheap to replace every couple years or so. I actually buy 3/8" ID in box quantity from McMaster Carr, but I have it on at least 4 machines. & will use a full box about every 3 years or so. Very seldom even need clamps on barbed fittings.
Do you have the big catch pan on the base of your mill? It's hard to contain all the splash, drip, of flood coolant on the table of a standard BP Clone type mill.
Loc-Line also has pliers but you don't need them & probably wouldn't want them if you bought a pair. Brand new line can be a wee bit of a pain to snap together. A little heat from a butane lighter I have found to work best.
I once purchased something ENCO had that resembled Loc-Line. Don't know if it's the same stuff they have now but it was a pure waste of money.
Also search ebay for Loc-line. The kits will probably be about the same money as ENCO. Especially if you can order enough other items to get their free shipping. I founs someone not lon ago on ebay that had extention pieces of the line only with a "Make Offer" deal I went 1/2 price on 20 pieces, They countered a bit higher, I bought!