1) Start with some polished mirror finish stainless from McMastercarr or Grainger
Polished Multipurpose 304 Stainless Steel Strip, Mirror-Like #8, 1" x 36", 0.0300" Thick
2) For the tighter radius pieces you will need a roll machine for a really nice job, I used a KAKA 3-In-1/8,8-Inch Combination Sheet Metal Brake,Slip Roll Machine and Brake Shear Roll Machine from Amazon which was roughly $300. Its also handy for making the 90 degree brackets and shearing the metal to length. The larger guide was just gently curved by hand.
3) Used 1/8" rivets from Pinball Life with a rivet setting tool from Amazon.
I made the uprights from thicker stainless I had lying around in my scrap pile so can't help you there! The uprights are 3/4" wide to match the dual screw pattern in the playfield.
A typical guide you start with one end, this will be your anchor point that everything else will flow from. Bend the metal to the rough shape you need it to be and place on the playfield using spacers to keep it off the playfield surface. I used some silicone post washers I was using during assembly.
Once you have the one end anchored, go to the next point and mark the centerline between the 2 screw holes in the playfield for the next bracket. Use a sharpie and mark the back of the new metal for that location.
Remove the guide back off, scribe a line at that location on the back of the guide so you have a vertical hole drill location. I used an old Bally guide that had 2 holes in it to place over the new metal to get my horizontals. Once you have your two locations, centerpunch briskly and then use a 1/16" bit to make the initial holes and then move up to 1/8" drills. You will be tempted to skip and run right to the larger bit, you are better off doing it in two stages. Once you have your two holes, clean off the burrs with a larger bit (5/16 for example) and place the guide back on the playfield.
Screw down your initial anchor point and with the guide in position, scribe the 2nd upright for rivet attachment holes using the freshly drilled guide as locator. I used a 90 degree pick and just wiggled around the hole, it will leave a clear round marking on the stainless.
Take both pieces back off, center punch the upright, drill and rivet together. Test fit making sure there are no burrs (use file) before hand and then proceed to #3
Rinse and repeat.
This is very time consuming; I had two days time making these two parts but they came out most satisfactory and I was moving at a good clip by the end. The metal brake is also very handy for bending the wire for perfect 90's on the wire ball guides.