I know I'm gonna get some negative feedback on this but here it is anyway
I have used Easy Off oven cleaner with great success... Used properly and paying attention not to let it sit for very long, will not harm the wood in any way. I've restored many milsurps using this process.. Others I've been able to slip into the dishwasher for a good cleaning but for the long stocked rifles, the Easy Off has been the ticket... I let it sit for around 30 mins then wash down with "hot" water.. I let it dry for a bit then check to see if another application is needed. Most times, the cosmo will be gone after the first try but I have had some that needed a second round with the spray cleaner.
I use the unscented variety since I do this in a downstairs shower (spare bathroom) and don't want to smell the place up or get the wife mad at me
I finish off my stocks with a hand rubbed BLO finish (boiled lindseed oil).