Cross-compile some ports on amd64 for i386

I have two FreeBSD-stable installations, on a newer AMD FX-8300 processor, amd64 and on an old one Intel Pentium-4, i386. Mostly I build ports from sources (with a support of portupgrade). I use these computers as desktops with MATE and some web and office applications among others. Mostly I build all ports from sources, all for AMD FX, but when it comes to an old computer, I have not several days to recompile some huge ports like www/chromium, for example. So, the reasonable idea comes to cross-compile some ports on FX and then transfer to Pentium system.

Are there any suitable tools and how-to's? Or it has more draw-backs than advantages?
I haven't tried myself but ports-mgmt/synth is supposed to be able to do such cross-compilation as well. Poudriere handles the cross-compilation as expected and it's recommended to use it in case the target system is very old and slow machine and compiling ports on it is not feasible.