Due to the very small size of most photo etch pieces, you don't need a lot of solder. You can use some NASA spec techniques. You'll need some small diameter, solid core solder, rubbing alcohol, cotton balls, and an iron with a small tip with flats ground around it. Use an alcohol-soaked cottonball to clean the metal pieces instead of using flux. Tin the iron tip and keep it clean through-out the session. Tin the etch pieces and they won't need anymore solder to connect them if you hold them together while heating. The tinning layers of solder will join when reheated to melting temps. It's important here to keep the pieces absolutely still while the solder is molten.
Practice this technique many, many times with left over scrap etch pieces before trying it with the valuable model pieces.
" 'Polls' are surveys of uninformed people who think it's possible to get the answer wrong." ...Ann Coulter