Soldato
I'm thinking its something like kopex you are trying to draw through: https://www07.abb.com/images/librar...s/pma-ex-system/396px-width/kopex-exb_396.jpg
If so then because its ridged inside then you might struggle I think!. One thing that does seem to work well (and I'm not sure what you'd get in lisbon thats similar). is strip the brown or blue out of a bit of 2.5 twin and earth and bend the end over, that gives a smooth end which can glide over the ridges, if its not ridgid enough then just strip the end of the twin and earth for a few inches and do that to one of the cores and then tape it where it comes out of the stripped end of the cable
If so then because its ridged inside then you might struggle I think!. One thing that does seem to work well (and I'm not sure what you'd get in lisbon thats similar). is strip the brown or blue out of a bit of 2.5 twin and earth and bend the end over, that gives a smooth end which can glide over the ridges, if its not ridgid enough then just strip the end of the twin and earth for a few inches and do that to one of the cores and then tape it where it comes out of the stripped end of the cable