What tools are you using ?
Some are very tight as you’ve found out .

Support the action so you can use both hands easily .Use the correct size slotted bit in a 3/8 ratchet on the lock nut side & a stubby driver on the bolt side , be carful not to slip.

The bits in an manual impact driver fit well but you may need a reducer for the ratchet or use a 1/2 inch ratchet .