Yeah and in particular stay out of the centre of the lane near intersections as that is where the build up is worst - it''s a good idea to avoid that anyways but in rain, especially as the first drops hit - use a lot of caution.
I'd certainly not drag your foot for traction testing but you should try braking in the rain in a safe situation to gain confidence. Build up slowly and more balance your braking.
You'll be surprised how well it does on normal pavement when wet.....
It's the slippy stuff like paint and metal that will give you a start.
Rain is no problem unless you run into vision issues with fogging and that can be very risky. Look at some solutions that are anti-fog and will bead up instead of blocking your vision.
Carrying a pair of clear safety glasses for rain is a good idea a vision can drop drastically in a storm and dark glasses won't help that.
Biggest tip - do not continue to ride if you are uncomfortable.....rain usually passes quickly ( the worst ones ) sit it out in a safe area. One with good coffee and fine looking serving staff make it worth while to take a rain break
I can recommend a very fine "wait it out place" on the road to James Bay
Complete with wireless and a cute wait staff.....an enjoyable hour out of a 1000k day.
But good for you to tackle rain as a new rider.....and ask for tips.