I use frame advance in VLC by using the ‘E’ key to seek a frame or just pause it whenever. Technically frame advance can hold on the same subtitle indefinitely, so I consider it in-bounds as long as 1) the subtitle pack I downloaded originally has it within that range (or, in the only case when the pack clearly missed a line, the range I create), and 2) the subtitle pack isn’t very obviously flawed (like starting a voice line multiple seconds before it’s actually said, continuing after another character is already speaking, or continuing after a very long silence; I’ve only encountered the first problem so far, and only once). Typically I try to get it as close to the voiceline as possible provided the shot isn’t a blurry mess.

TL;DR: the vibes™

If you specifically are using some other subtitle pack whose timings are really messed up, you should be able to go into the human-readable file and change it.