Unfortunately, it's not simply a matter of growing some balls.
The better rain riders are those that have mastered the ability to basically let go of the bars after they've countersteered.
This method helps you go fast in the dry too, but you can get away with more pressure in the dry.
You don't actually let go of the bars, but you need to basically be holding yourself with your legs and core muscles.
Practice tip: While sitting in a chair in a riding position, close your hands tightly around pretend handlebars. Get your butt off the seat slightly and then push one arm forward (right for right turn, left for left turn) as you drop your head and shoulders into the corner... and at the same moment relax your hands so they are still curled around the "bar", but loosely.
While your "hanging off"... feel your legs and stomach muscles holding you up. With no actual handlebar, you obviously can't hold yourself by your arms. Get used to this feeling and strive for it on the bike.
Now... pretend you're coming out of the corner. Feel how you must use your legs and core muscles to bring you upright again.
That is the feeling and method you want while riding... especially in the rain.
If you are using your arms to move yourself around on the bike, you will always be fighting what the front wheel wants to do... which is to self correct.
Another good practice exercise is the "chicane". Sitting in a chair with no arms, put your legs out to the side like on a bike. Practice moving back and forth over the chair as though you were doing a left/right/left sequence of turns.
Keep your hands out in front on pretend bars and get used to the leg and core muscles involved in smoothly going back and forth. If you're doing it right, you should find it kind of hard.
Fact is... riding a bike fast takes a lot of hard work.
Remember... unlike a car, the rider is a big part of the suspension on a motorcycle. If you don't actively move around on the bike - at the right times - then you will always be a hindrance to your suspension.
The good riders will always be a step ahead of their bike. In other words, if you're going into Turn 3 (a sharp right), your lower body should be in position before you countersteer. This way, when you press on that right handlebar, all you have to do is let your upper body "fall" in after the press. Push... fall.
If you "hop off" the seat as you are countersteering, you're never going to be smooth... wet or dry!