How do you clean your synthetic brushes?

Another brush bites the dust. And the title is posed as a question and not a rhetorical one. How do you clean your synthetic brushes?

I love my Real Technique brushes: they are synthetic, meaning can be used with many mediums, they perform very well, they are multi-tasking, and they are of good quality. Good quality? I still think so, considering the cost (this is not Koyudo, Hakuhodo, or Chikuhodo we are talking about), even after the demise of the above well-worn Stippling Brush.

I got this one about three years ago. It is one of the most well-used brush in my collection for foundation blending and cream blushes. With synthetic brushes, oil-based makeup seems to cling onto the fibers and the product can get trapped deep in the middle/base of the brush (especially if the brush has been used for a long time). So, occasionally I use my cleansing oil to loosen up all that build up before washing it thoroughly with water and soap. I do this every other day, slightly more often during the cooler months.

It started with just a little tuft. Later on, a bigger chunk of hair came off.
So, am I too harsh with the brush? I have the feeling that the cleansing oil is the culprit. Here's why.

I am skeptical about "dry upside-down or at the angle" advice because, as we all have learned in basic science, water will travel towards the ferrule by virtue of capillary actions. The tiny space between two fiber hairs is so minute that it provides the capillary action. In fact, I'm willing to bet that capillary action is how liquid products travel and accumulate into the middle of the brush and further down the ferrule.

To reinforce my argument about the cleansing oil as culprit: I use to dry my brushes right-side up (i.e. the fibre on top, handle on the bottom) in a cup. All of them, including the Sonia Kashuk ones, which clocks almost 10 years. The ferrule of these brushes were subjected to longer term of exposure to water with capillary action and gravity. Yet, they are still functioning, the ferrule still intact with little shedding as the time goes by. Only when I learned about the "proper" way of air-drying brushes that I started to lay them flat for drying (but then again, capillary action still happen, it happens regardless of the direction of gravity). On the other hand, you may have noticed that cleaning natural fiber-brush is easier than synthetics; all I have to do is shampoo and condition, no cleansing oil needed. My synthetic brushes have to endure cleansing oil insult, on top of water soap, thus the theory of cleansing oil as the culprit of the weakening ferrule.

Finally, from the design point of view, if I were a brush designer, I would choose a ferrule glue that is somewhat impermeable to water or maybe withstand regular cleaning with water. I can understand if water-based glue is chosen for natural fibers -- some organic solvents can eat up keratins/organic proteins. If the fiber is synthetic, however, the more reason to use oil-based glue as it does not jeopardize the integrity of the fibers and the glue is more durable than water-based one. Oil-based glue cleansing oil = dissolution. Maybe I'm wrong, these are all just hypotheses.

This is a reason why I'm a bit weary about investing in fluffy foundation brush (the perennial fave such as the ones by Sephora or Louise Young Super Foundation Brushes), I can already imagine the foundation build up in the middle of the brush that will be harder to clean as the time goes by.

I'd like to hear and learn from your experience & tips, especially from brush experts/afficionadas. Please leave your comments down below.

Update:
Real Technique reached out to me and offered a replacement brush right away, without me asking. Thank you, Real Technique!!