After using 105 and then 205, you'd be best off performing an IPA wipedown. I'll link to a thread further down this post but essentially you are removing any and all oils & residue left on the surface of the paint after polishing. Heed caution though, you just spent so many hours correcting the finish of your car and should only use the softest, plushest microfiber you can get to perform this step as to not add marring, swirls, or even scratches to your paint.
As for sealants, I selected a sample size of both Blackfire Wet Diamond All Finish Paint Protection and Wolfgang Deep Gloss Paint Sealant. If you're doing your own personal vehicles, with how long the products last, and how so little goes such a long way when applying the product, I suggest trying the sample sizes first. The only other sealants that I've been interested in trying are Menzerna Powerlock, Wolf's Hard Body, Optimum Opti-Seal and Meguiar's M21, while others may suit your fancy better than the ones I just mentioned, I'll leave those to others and suggest you look into these.
When I do my vehicles, I'll apply the sealant, then apply tire gel and whatever else needs doing to occupy 30-45 minutes then buff off. It's important to let the sealant 'cure' anywhere from 4-24 hours, the longer the better, but some times you can only do it for so long. It's important that the vehicle doesn't get wet, and since it is the season, try and keep it indoors to avoid pollen contamination as well.
