My preferred method is a roll of fencing as a mobile and less visible race for the sheep so that if the ewe decided to try to high tail back out of the pen you have an extended area in which you can funnel the sheep back in. it may only fool her the once but have used it many times with my sheep. by having a roll of fencing that is mobile you can simply roll it up until you reach the gate. Have had a wiley old ewe who would try to find a cunning alternative to capture every time but she finally (mostly ) accepted the race.