Parakeets using new perches / toys

by Tony

So, I have 4 parakeets in a huge cage and 2 of them are new, the 2 of them are being smart and are using the natural / sand perches / toys to take care of their nails / beak, my other 2 parakeets that i had from the beginning doesn't know how to use the perch, it doesn't try to use it with it's beak or anything, it just try to nimble on it's own beak, i doubt that it's beak is hurting because it still eats and climb the cage, i don't want to be forced in a position to take it to the vet but i will if i must, i'n trying to get my 2 older parakeets to use the perch, how do i do this?