I think the solvent you read about is the activator that comes with Loctite "All Plastics" cyanoacrylate glue:
http://www.loctiteproducts.com/p/sg_plstc/overview/Loctite-Plastics-Bonding-System.htmThere are probably other brands of the same stuff where you are that might be cheaper.
The activator is Heptane (or n-heptane) and it can be bought separately but it might be harder to find. Loctite sells it as 770 Primer which is available in 100ml bottles but it doesn't appear to be stocked by the major hardware stores here.
I just buy the two part plastics glues with activator, either Loctite or Selleys (a local brand). And it works well enough. I find I can get the joint apart if I need to but I haven't had too many occasions when the joint comes apart when I don't want it to.
Like Wiking if I'm swapping heads or arms I use a pin vice drill and use pins with the glue for a firmer joint. Some people use steel dressmaking pins but I just use whatever plastic pins I can find, Spare flagpoles, bristles from a dishwashing brush, etc.
With HaT's old plastic I haven't done much except use some of the spare heads, which have pins of course, and glue some bits of a roman shield to another figure. No problems with these.
I've also used this glue on HaT's new plastic, and Strelets, Italeri, ESCI and Waterloo 1815 figures to change poses and change weapons. I have also cut Italeri figures in half and swapped over the upper bodies. These were glued without pins and they're rock solid.
One thing I don't use this glue for is fixing Airfix horses to their bases, I weld those.