I am getting ready to rig my Cigarette Bullet and would be interested if anyone had any pro tips on getting everything sealed up good on the transom? Of course I understand the basics of sealing everything, but thought some of the pros might have some special procedures that they have found to work. Thanks!

Im not a "pro" so take it for what its worth
If your dealing with the 3M 4200 or 5200 when sealing up "things" then you can easily wipe off the excess with some WD40 on a rag...makes things easy. Rubbing alcohol is also good for cleanup.
If this is a totally bare transom then im sure you "sealed" the insides of all the cutouts with some fiberglass resin...if not then now's the time to do so.
On the transom assembly rubber gasket....they say to install it dry....but that never sat right with me so i usually smear it with some red-n-tacky grease for my own peace of mind. Ive seen some coated in silicone as well but your just making it harder to take it off later.
Oh and if you want very clean joints around things then first install the part dry...then tape off around it on both the part being installed and around the transom...then take the part back off and apply the sealant (4200/5200 etc) so when you both it all down and the wipe off excess you peel the tape and you have a perfect bead around it.

Im sure there are other tricks people use and i always love hearing them

Any holes that are drilled through the transom seal with resin. I dipped pipe cleaners in resin for the smaller holes and brushed it on the larger holes. You can see some of the holes in the blue tape for the pipe cleaners.

When I was helping my Uncle restore an old wooden boat, he used a thinned shellac that soaked into the wood fibers on the outside of the hull before applying the marine varnish. I see the problem with just using resin is that over time it can wear off and it's too thick to absorb into the wood itself. Anytime I make a hole, I'll thin some Rust-Oleum and let it soak in real good and then use 4200/5200 sealer even for small screw holes. Kind of a poor man's wolmanizing.

I’d call and ask Fountain how they did it back in the day.

Ouch !

I actually mixed it less than the 2% and made a "cold" batch just for this. It took a couple of days to cure. I've treated a lot of wood with just resin and have never had issues soaking into the wood. I do this to the wood under my upholstery and works just fine.

For all the screws or through bolts I’ve always used life seal. It’s easy to use and when you ever go to take it apart it comes apart a lot easier than other things I’ve used

https://www.merriam-webster.com/dictionary/wisenheimer

If you've resin sealed (epoxy is my choice) all the transom cutouts where wood coring is exposed = good !
As far as a sealer goes if you never , ever plan to take anything off again or you sell the boat to someone you hate and want to punish them then use 5200.
I wouldn't even use 4200 .
I still recommend Life Caulk (non-siliconized) for sealing stuff and bedding hardware including around the transom plate .
It's durable and dismantleable years later.

On my little boat I recently stripped the deck of everything for painting and discovered that I had accidentally used the siliconized version of Life Caulk on a lot of hardware and fittings (Life Seal) and it was a total PITA to get off. 4200 would have been even worse .