How I would do it is to change the mirror in /etc/slackpkg/mirrors and do an update. Then download the 32-bit compatibility layer and libraries (for current) from Alien Bob's site and then in the directory that these are in do an
upgradepkg --install-new *.t?z
That should be all there is to it. There is a lot more maintenance involved if you are running current as the core programs are likely to change more often.