turn on SV_cheats 1
then bind "ALT" to "+ALT1"

bind ALT "+alt1"

upgrade the portal gun and paint gun

bind "Q" to "nextpaint"

bind Q "nextpaint"

test if alt switches between the portal gun and paint gun

test if Q makes the paintgun change between each gel

and remember to do "save_console 1" to save it for the next levels, it wont save when you reload the files tho

upgrade_portalgun

upgrade_paintgun

bind ALT "+alt1"

bind Q "nextpaint"

and if switching the guns dont work, do "BIND ALT "+ALT2"

that this does sometimes doesn't work

edit: also before upgrading, do get the portal gun and paint gun

give_paintgun

give_portalgun

the game can sometimes crash, be carefull