Hose them off with a harsh water spray. Repeat as needed.

They're soft-bodied insects and are easily damaged by the harsh spray. But you must repeat because, even if you miss just one, she can re-populate the plant by giving birth to an already pregnant youngster every 20 minutes!

The sharp water spray knocks the wee buggers off the plant and they then cannot find their way back so they die. Whether that spray actually kills many is not easily determined, although the studies I've seen suggest it is not a major method of elimination.
Some people, that know little about Aphids, may tell you that the Aphids knocked off by that sharp water spray simply return to the plant, but they do not. What does happen is that the next generation of Aphids will move in to replcae those you knocked off.
Aphids prefer plants with lush, green growth so they are found most often on plants fed too much Nitrogen.

Here is a link that might be useful: Aphid management

Why did you not just order preying mantis eggs this year?

Keep iin mind that Praying Mantids capture and eat all kinds of insects, beneficial as well as pests, including other Praying Mantids.

I tend to doubt that mantids are very helpful in controlling large aphid populations. They tend to be more attracted to victims that move around more than aphids do.

I'm one of who is not thrilled when I see these in my gardens. I've seen too many piles of empty butterfly wings on the ground. They hang around the flowers that are most visited by bees and other pollinators...if I move them to another location, they return to that favorite spot!