A lot of Rains like to use F21 and F32 as a sort of second hit mixup in the neutral, although F3 can be reacted to and blocked accordingly, the F2 and F3 animations do have some similarity making it a bit tough for some. Another option I have found is to block overhead, immediately input an armored move after blocking a hit, and continue blocking overhead - if timed correctly you will block the entire F32 string, and interrupt the gap on the F21 string. This option obviously also allows you to hit them if they go for the low instead of just blocking, but don't overuse as it can be baited out if Rain decides to not do an entire string.
