Thrips are a bitch to get rid of and you will encounter them if you collect plants. You can buy or trade an infected plant without knowing because thrips inject their eggs into the plant tissue and the adults are super small to spot. In my experience they are very difficult to get rid of, but it is possible if you are persistent with the treatment. If you can afford it, it is better just to throw away the plant and get a new one. These bugs will cause you grief, test your patience and the work can be overwhelming to deal with.
The risk of keeping an infected plant around is that they will jump to other plants unless you quarantine them. I quarantine the plants in a clear plastic tote with a clear lid. The clear tote will allow light in. Open the lid to allow air in every couple of days. Make sure to use a high tote or storage box to prevent the thrips from jumping to other plants.
The picture below shows signs of thrip damage. I highly recommend to cut back the foliage and cut away the damaged leaves because their larvas are still hanging on there.
There are a few methods I've used in the past to kill thrips. Certain methods will work better on some plants and they are listed below. Whatever method you choose, ensure that you repeat the treatment every 3 days for the next two weeks to break the thrip life cycle. Also, water your plant first before using any type of treatments including insecticides.
Spray infected plant with 99% rubbing alcohol.
Don't spray the echeveria or any rosette or any succulent with powdery leaves as they will get damaged.
Wash and Rinse
De-soil the plant and wash periodically with water over the next few weeks until the new growth has no signs of damage. De-soiling the plant will prevent root rot and thrips from hiding in the soil. You can up-root and put the plant in a small pot as shown in the picture below. This allow you to spray the plant often with water to wash away the bugs. You can also pour a little bit of water into a cup and rest the plant on top with the root hanging downward touching the water. This method will work with echeveria succulents. For hoya plants, you can put them in a wide mouth vase with some water.
Brew chewing tobacco as a tea and use to spray the infected plant. Too much usage of tobacco tea can stunt plant growth.
One teaspoon of dish soap per one quart of water. Shake well and spray the infected plant. This is my favourite method because it's simple, cheap and effective.
Don't spray echeveria plants or any rosettes or any succulent with powdery leaves as they will get damaged.
After 20 minutes of spraying my infected Orbea plant I was able to collect the casualties. Unfortunately, some thrips will survive the first spraying but they weaken and will most likely die after a 2nd spraying. Make sure to rinse off the soap with warm water about 20 minutes after treatment.
End-All By Safer
End-All solutions sometimes work and will kill the larvas. This solution won't burn most echeveria species if you leave the plant in the shade after spraying and away from grow lights for 12 hours or until the solution is completely dry.
Get the concentrated End-All solution so you have control over strength and dilution.
Slow Down Breeding & Feeding
To slow down thrips or any sucking insects from breeding too fast or feeding too much, create a humid environment (put plant in a dome) or mist plant often with water. In the summer, I put the infected plant outside and let mother nature deal with them. When you leave the plant outside there are beneficial insects that will attack the thrips, mealies and aphids. Let the rain wash the bug away. Wind will blow them away and they don't like the hot sun beaming on them. Rain water, good air flow and sun will aid your plant health. Before taking your succulent out to full sun, ensure to leave your plant in the shade for a few weeks to acclimatize them, otherwise, they will get burnt.