Tuning a string instrument with well temperament

When I practice the cello, sometimes it is noticeable that, when playing big chords, they tend to be out of tune - the C string sounds a bit too flat. This is the issue of tuning by 5ths for any string instrument. Is there any way to tune a string instrument with well temperament without the need of a tuner, or the tedious way of bringing 5ths closer together? I'm looking for a relatively quick and efficient method of tuning only with the cello itself? (no tuners or pianos)