As you're in the US, I'd suggest Kester EP256* (63/37), and Kester RF741 flux.
* Kester only sells it in large amounts (i.e. 400 - 600g tubs & cartridges), but CML Supply breaks it down into 35g syringes for the hobbyist/repair specialist market (here). The RF741 comes in 30g syringes & 100g jars from Kester. CML offers a smaller size of this as well (here), though the 30g size is more cost effective (3x the cost, but 5x the amount).
Strongly second the above. Excruciating detail below (TL;DR at end) ->>>>
I have tried probably 15+ different pastes over the years. Various leaded and lead-free options from AMTECH, Sparkle, AIM, MG Chemicals, Kester and others. EP256 is far (FAR) beyond anything else I've tried.
The stuff about keeping paste refrigerated and using within a short time only applies to medium to large companies with tightly controlled processes or those that need a chain of custody/QC. For everyone else, it's unnecessary. I get solder paste shipped unrefrigerated by ground service. I buy expired paste. I open it and don't refrigerate it. I place boards that were pasted 2 or 3 days before. I open a tub of paste and keep using it for weeks or months without bothering to refrigerate between uses. I put unused paste back in the container once I've pasted the boards for the day. Of course, I don't do this as a matter of course, I am just saying that sometimes shit happens... you come in after a long weekend and someone forgot to run the last few PCB's through the pick and place. So you say "Hmmm, still feels tacky... let me see how they come out!" - and they come out fine.
So I've pushed the boundaries of paste, and EP256 is head and shoulders above in terms of results for regular use and in terms of how forgiving it is. EP256 performs flawlessly. I assume because of the alloy and the flux it uses. It requires no post-reflow cleaning, I have no issues with tombstoning parts, components center perfectly. The cost of solder paste is so low on a per-board basis that it's not worth trying to save money on paste. We do several thousand PCB's per year and we go through maybe 4-5 500g jars/year. At around $60/jar it works out to a few cents per PCB (each with 100+ pads). The wrong paste can really cause problems. I just this week finished fixing a few hundred boards that needed reworked because they didn't reflow correctly and got put aside. I didn't get around to reworking for over a year, and it took me 2 days to fix them. And I've had similar problems in the past when we tried a new paste only to get tons of passives tombstoning, or the flux wasn't very active and resulted in lots of bad connections or parts that didn't self-align during reflow, etc.
For flux, are you looking at something for rework? My go-to is Kester #186. I have tried various no-clean fluxes (like Kester #951) and they just aren't "active" enough, or they are so thin they almost immediately evaporate when hot-air or soldering-iron reworking. 186 is a rosin flux, active enough that it reflows/remelts solder beautifully, but is thick enough that it doesn't instantly evaporate from the PCB.
I have tried tack fluxes. MG Chem #8341 is OK. The upside to tack flux is you get a lot more working time on the PCB. You can remelt a connection probably 2-3 times before it melts away from the connection and you need to add more. #186 might get you 2 melts with an iron and is OK for hot air. #951 you have to immediate hit it with the iron or it evaporates, and if you are using it on 2 sides of a SOIC, for example, the heat from reworking one side will evaporate the flux from the other. The thin no-clean fluxes are useless for hot air rework. My favorite tack flux is AMTECH NC-559-V2-TF. The problem with all the tack fluxes I've tried is they come in syringes which really need an air dispenser to work. Even with a 12 gauge nozzle, you have to apply a lot of force to the plunger to get any flow, and when it starts to flow you get a ton of it on the board. With a pneumatic foot-pedal operated dispenser, the NC-559 is bliss. But 90% of the time for a quick fix - it's the #186 I reach for. I have tried many other fluxes - rosin fluxes from the dispenser bottles hardens and turns into a mess. Paste fluxes in jars get everywhere and you throw away most of it. Many of the jelly-like fluxes turn to brown concrete on the board if you try to hot-air rework with them. So I stick to the 186 and NC-559 in 99% of cases.
Probably more detail than anyone wanted, but it is what it is.