Standard way on 3-side of clave: rimshot on 2& , abanico, rimshot on 1
on 2-side of clave: rimshot on 3, abanico, rimshot on 1
Apart from that I go with my feelings, which are usually quite conservative, since this transition often means I'm about to start singing a coro

so I don't have much spare brain for playing fancy patterns on the drums!
I think it's important to understand the whole band context for the transition.
For example, 2 bars of 1/8th notes on the bell and hembra is a great way to bring in a really high dynamic, but it wouldn't work if you then went to mambo bell and no campana.
Alternatively, a figure that's quite light but uses the mambo bell gives the listener a clue that it's coming in, e.g. roll to muted strike on 1, flam the bell on 1&, muted strike on 2&, bell hit on 3, abanico beat 4 to bell ride pattern on 1 of next bar.