I understand your predicament with shops.

One trick is to use the bladder as a sort of squeezy.........put oil in the shock body, give the bladder a squeeze and let it suck the oil in. After that, careful positioning of high points and you can bleed all the air out with a bit of a squeeze and suck here.....and a tap with a mallet there.

One thing that may cause some shock builders an issue is that air can sometimes lurk in the valve under the shim stack. Just pushing the valve through the oil slowly doesn't release it as the shims never open and the oil goes through the bypass or low speed orifice. A strategically aimed sharp crack or two with a mallet opens the shims enough to release the air.