I'm having issues trying to figure out how to pronounce "winningG" so that the hard 'G' at the end (as in bug) is heard without a schwa on the end.

Do you mean: winninga?

Usually this is heard in transit between two vowels, not as a final consonant. The familiar example is the much-referenced (mostly by people trying to be funny) New York pronunciation of Long Island (LonGisland).

Renember that |ŋ| is a sound of its own, nothing like the bare n of winnin'.

@Cascabel It's like finger without the -er.

I associate this with the LonG Island accent (another example). There is a large Jewish population in that area and it is possible that either the Jewish parents originated from there, or this is an element of Yiddish influenced pronunciation.

Quite notably, the group I like to call Forrest Gumpians, for one, meaning the group with that particular Mississippi accent would be on the list (huffpost.com/entry/tom-hanks-forrest-gump-accent). There are so many groups of Americans with different accents and pronunciation, as well as interpretations of what constitutes a hard G (e.g., if it includes a plosive), not to mention all those that sometimes do and sometimes don't, as opposed to those that never say the G but pronounce -ing as just "in" (e.g., *winnin', stealin', etc.), so your question needs more focus.

This is also an element of regional British pronunciation. For example, it's how Prof. Brian Cox pronounces some of his -ing words – usually, it seems, when he's emphasising the syllable. You can hear it right at the start of his recent Long COVID Youtube clip, and also at 3:16. It's very soft (and @Cascabel: no schwa) – not quite a glottal stop, but I'm not really sure what the sound is called.

I don't know to what extent British dialects are still detectable in the US but, as Chappo says, it is one characteristic of the Black Country dialect. "There is no NG-coalescence, so singer rhymes with finger, with both commonly pronounced with ŋg~ŋk. Indeed, the accent can be analyzed as lacking the phoneme /ŋ/ with that sound instead being regarded as an allophone of /n/." Wikipedia.

@GArthurBrown Please see TChrist's answer, as well as Lambie's & Robusto's comments..yeah it is "long guy land" in Long Islandese, but that assumes a liaison between 2 words...you cannot see my deleted answer, but the answer from TChrist is worth a read.

@Cascabel Of course it is more pronounced when intervocalic, and this may be true even additional regions as well, but the accent that pronounces it when word final is the Long Island accent, who will indeed say "lonG," among those other accents listed here in the comments.

@Lambie, it's kind of like "winninga," with that type of pronunciation of the G, but they don't really have a very noticeable vowel sound at the end of the word.

Thank you so much for the comments, everyone! I appreciate the food for thought.

@ChappoHasn'tForgottenMonica Yes, the examples from the video you linked to are exactly what I'm talking about, except that the people I'm talking about aren't British. But it's the same sound.

The whole point is many Long Island natives do pronounce the hard g. To me, it sounds like: Longai Island, gai like Moo Goo Gai Pan. I would argue you can't "hear" the i there unless it is preceded by something else.