only allow your kids to have bunks when they are old enough to make it themselves

DSS has to make his (he is 11) and i sometimes give him a hand, man its tricky, no wonder he takes so long...
I do the same as you, crawl over the bed...
I think the trouble is that we have a 'good' mattress for him, the bunks we had when we were kids were like foam and so would pull up and move easier

GL