I used this tool to layout my 7x4 Multiboard Wall. I used Sunxeke Flat wall anchors https://www.amazon.com/dp/B0C737Y5VR?psc=1&ref=ppx_yo2ov_dt_b_product_details (no affiliate link). The tool lines the anchors up pretty well. You can drive about 1/3 of the anchor in until it is flush with the tool. You then remove the tool (that is why there is a cap) and finish driving the anchor into the wall.
I am using the 8mm offset mounting method. My technique is to start at the upper left corner location with the GuideMain and GuideTop pressed through the multiboard. I slot one of those anchors into the guide. After leveling the board, I lightly hammer the anchor into the drywall until it is flush with the tool. You can then remove the multiboard, separate the tool into its two parts leaving just the anchor firmly in the drywall with about 8mm still to go. Just takes a couple more hits to completely seat the anchor. I would then screw the proper offset mount into the anchor.
This gives you a fixed point to temporarily install the multiboard repeat the process at the other end. That is where the installation alignment tool would come in. I place the solid octagon in the upper right hole in the multiboard (with the flange flush with the wall), and I would then place the next section of multiboard on the right side octagon and hammer the anchor in. I don't like putting a ton of anchors in the wall so I only anchor 1 side of a DS, and both holes on one of the Quad's. You then remove the boards and alignment tool, finish driving in the anchor, screw in the mount and repeat the process.
I knew at the time, I should have taken pictures as I installed my board... I have attached a couple pictures illustrating my technique. You can find me on the multiboard.io community pages if you have questions.