Don't inflate with CO2 if you have Stan's sealant in the tyre already, as doing so has a tendency to turn the sealant into coagulated lumps, presumably due to the sudden temperature change.
If you have to seat the tyre with CO2 do so before you add sealant (and without the valve core in place) then add the sealant and inflate with a track pump (hopefully), again with no valve core. Then remove the pump, seal the valve with a finger and get the core in without losing all the pressure. Sound faffier than it is.
If you have no compressor then the Coke bottle pneumatic accumulator method works best of all - all you need is a 2 litre Coke bottle, two presta valves (one with the core removed) and some 5mm ID plastic tubing.Here's
how you do it - you can make them fancier by adding a valve etc. but they all work the same.
If the Coke bottle gets old and/or scratched then throw it away and get a new one - I've never needed to pressurise it to above 4 bar to get any tyre to seat with the help of a little soap solution on the beads.
If you want to satisfy yourself that a Coke bottle will easily withstand 60psi+ then fill it full of water and pressurise it. I've had them up to 120psi but only water filled, not with air........