Yepp go with a easy going jelq routine as already mentioned. Don’t go in and do it too erect; 60- 80% erect as already said is your best and safest bet.
Warm up for 5 minutes at least and go for it, start off with no more than 50- 60, 3- 5 sec jelq strokes and ramp up the reps after a week or two by 10- 20 jelqs. If you’re uncut I’d recommend doing dry jelqs, if not use some lube and do them wet.
The point of not being too erect is to prevent injury and actually getting some good blood flow going+ 100% erect jelqs are more risky regarding getting injured.
Then warm down as heat seems to be key, especially in gaining girth.
Edit; Also be on the lookout for good signs of good penis health like frequent and nightly erections, if they start to get less and/ or less hard you’re probably overdoing it and need to ramp the intensity down.
Start with a 2 on 1 off schedule or maybe 1 on 1 off. This you’ll have to figure out for yourself.
Best of luck.