If you want to REFLOW solder SMD, then yes, you need solderpaste.
Just search for ‘solder paste’ on ebay/aliexpress - make sure you’re not buying just the ‘flux’ (yellow creamy like stuff).
I’ve only used the blue 50g pots from mechanic so far (still got 1 pot unopened). Not stellar, but does the job for prototyping (keep them in the fridge after opening!). Little coarse and the residue - while being marked as ‘no clean’ - is better cleaned off after the reflow process with Methylated Spirits in an Ultra Sonic Bath (yes, another piece of kit you’re going to want if you go down that path).
Do you have the stencil yet?
Do you have made yourself acustomed with the process?
You got the toaster oven yet?
One that can ramp to 350 deg C within 2-3 minutes?
..
Be very careful if you manually reflow anything in the 0.5 mils pin spacing category or below. That’s the range where I start to get problems.. example would be something like a SSOP 10 pin with 0.5 pin spacing package.
Oh and your stencils, for manual work.. set the solder paste clearance to 0 for a start before you plot & then order the stencil:
