I think strong arm tactics are probably a mistake long-term.
DD was prescribed her inhaler at around this age and we started off forcing her to take it until she was actually frightened to even see the spacer. She wouldn't even let me hold it to my own mouth and would bat it away because she thought it was something to be frightened of.
We had to slowly reintroduce it, by arranging for it to appear around the house e.g. in her nappy box, on her dressing table. We would always make sure we ignored it at first. Then I would let her see me pretending to use it, demonstrating some nice deep breaths. Gradually I would just let her play with it, examine it and if she brought it up to her face that was great. Teddy and dolly always had their inhaler.
It took a few months but she would then happily take it. If she didn't one day, we didn't make a big deal about it we just said 'ok, we'll try again later'. Many many times we've done it whilst she slept.
A GP recently told me that when children have a nebuliser they have an entire blue inhaler in one go. When they are having one/two puffs the amount is tiny, particularly with very young children as the amount inhaled is minimal.
Its worth the long term approach imo. DD at 2.3 now has brown and blue inhalers morning and night and blue on demand. Generally she's pretty good at taking them (much better than she is at teeth brushing for example). We are more strict on the brown one because the dosage builds up over around 10 days so needs regular doses to be effective.
p.s. There was an episode of Get Well Soon on cBeebies where Dr Ranj prescribes an inhaler, might be worth a watch if you can track it down