Francis Yaconielloon Stack Overflow • Recommends
On “Django form with ManyToMany field with 500,000 objects times out”
You need to create a custom widget for this field that lets you autocomplete for the correct record. If you don't want to roll your own: http://django-autocomplete-light.readthedocs.io/
I've used this for its generic relationship support, the M2M autocomplete looks pretty easy and intuitive as well. see video of use here: link to this video
After reading your comment about needing it outside the admin, I took another look at the django-autocomplete-light library. It provides widgets you can use outside the admin.
from dal import autocomplete
from django import forms
class PersonForm(forms.ModelForm):
class Meta:
widgets = {
'myformfield': autocomplete.ModelSelect2(
# ...
),
}