It's not easy, but if playing riffs clean is what you want, it's worth taking the time to get it right. Me, I think a cleanly-articulated riff sounds so much better than one that's not, but for some people it's not that big of a deal. Some days it's all I work on.
For the finger tip, you could just practice a basic Pentatonic shape (with distortion of course), say 4 notes, 1 on the e, 2 on the B, and 1 on the G, and focus on the fingertip muting, but also how the 3rd/4th finger kind of 'drapes' over the higher string just as it comes down to fret its note.
Another thing I work on, is just releasing pressure from a note, as opposed to completely removing the finger. It's more economical, and also helps with muting.
And keep in mind, the fingertip takes care of the next string, therefore the palm only needs to catch the rest of them. And it has to move across the strings as the riff does.
And another one to work on is the 'finger-roll' when playing 2 successive notes on adjacent strings, on the same fret. Which if on the e-b strings, sometimes sounds fine, if they overlap.
View attachment 8877
This is from the solo in
Carry On Wayward Son, and in measure 26, if the 2 notes @17 blended together, that's one of the types that doesn't sound bad. Lots of solos have that type of riff where those notes are not separated.
It's certainly a lot of stuff to focus on, but I think your playing benefits when you strike that perfect balance between no overlap, and also no gaps between the notes.