(Assuming that finding a slower Minyan is not an option, and that you are using the Ashkenazi/Chassidich version.)
Take a 2-pronged approach:
- Don't plan on saying it all
Prepare the shortest chapter of that day; very often it's the Pizmun - the one towards the end recited by the congregation and Chazzan.
Spend a few minutes before Selichot (or while the congregation is saying the first pieces) to understand what it says.
Then say it at your pace - irrelevant of where the congregation is holding.
The parts you should say with the congregation are the 13-Middot (Hashem-Hashem, etc.) and the 4-5 Pesukim right after, which are the main Selichot. The "long" Selichot were introduced later.
If you pencil in the translation/meaning while you are preparing, then over the period of a few years you will have most of the Slichot under your control.
BTW: Once you get the hang of the language, you will find that you understand most Selichot even without preparing, as the themes are recurring.