Swirls are inevitable, in order to minimize swirls you must wash your car extremely meticulously.
Are you using a grit guard in your 2 bucket technique? I began using 2 grit guards for both soap and water, but now I only use the grit in the water bucket. From experience, I am able to remove 99% of the debris in my rinse bucket while saving myself 1 gallon of soap each wash (grit guard occupies about 1 gallon in your bucket)
Here's a tip that I've come across from experience. I use a microfiber wash mitt and when I reach the lower panels (lower doors, side skirts, rear bumper, dirty section), I lightly drag sections of my mitt to remove dirt, then flip over and use the fresh side for more pressure. Refer to my picture:
The red line is where you want the mitt to touch the panel. You want to drag the mitt across the panel
only on the red line by making a "gun" with your index fingers. I don't put my hand in the mitt, I just hold it. Angle/half-fold the mitt so you don't get the fresh sections of the mitt dirty.
You don't need to use pressure in this step! You just want to gently wipe away the debris that the hose didn't get rid of. After you've done all 3 steps, flip the mitt over and now you can use pressure and thoroughly clean the panel. Then, rub the dirty side of the mitt against your grit guard to clean out the debris. If done right, you should not see any color change (dirt) on the pressure side of the mitt. 95% of the dirt should be on the side where you 3 sectioned the mitt.
If you want to take it up a notch, invest in a pressure washer and use a foam cannon to help get the debris off before using a mitt. The 3 section mitt technique I used has minimized swirling for me when I never had a pressure washer. I still use this technique regardless.
Are you using a premium microfiber when you apply Opt spray wax? Did you wash off all the debris before? Turning the microfiber cloth frequently will minimize swirls from leftover debris.
If you don't plan to correct swirls after claying, again you must be very meticulous about your process. The dirt embedded in the clay can swirl up your paint if you use too much pressure, worse on a black car. Go slow; use a softer clay like Riccardo Yellow, and use light pressure on a surface treated with a generous amount of clay lube. Fold the clay frequently, less dirt = less swirls. Resist the urge to start going buck wild claying large portions at a time quickly unless you plan to polish after.
Investing in a PC and pads would be a wise choice for the long-term. It'll pay for itself very quickly if you baby your car.